吴国桢離台后来一直在美国居住，从事教育和写作。1984初年曾接受《蒋经国传》作者的采访，披露了大量当年与蒋氏父子尤其是与蒋经国的恩怨情仇。1985年6月，吴国桢在美国病故。

In an open letter to the National Assembly dated February 27, 1954, Dr. Wu appealed for consideration and debate upon six cardinal points. The first concerned the dangers of oneparty rule.

But the operations of the Kuomintang itself are financed, not by contributions from Party members, but by the Government treasury, or, in other words, by the citizens of China. This practice is not to be found in any modern nation save the Communist and totalitarian states. Speaking from inside the Kuomintang, it is also modeled after the so-called "centralized democratic system" of the Communists. That it is "democratic" is totally false. That it is "centralized" is sadly true. In order to put genuine democracy into practice, we must have at least two major political parties . . . The present methods adopted by the Kuomintang in government are entirely devoted to the purpose of perpetuating its power. It is directly contrary to the fundamental principles of modem democratic government.

Dr. Wu's second point concerned the devastating influence of Chiang Ching-kuo's agents upon Army morale.

The armed forces of a nation should belong to the nation so that they will not be made loyal to only one party or to only one person, thus creating forces for feudalism and possible civil strife ... But inside the armed forces of our country now, there is not only Kuomintang organization operating in secret, but there is also a Political Department. The so-called Political Department is entirely modeled after the system of political commissars of the Communists. Ever since the establishment of the Political Department promotions in the Armed Services have not been based on the merit of the individual but on his relations with the Political Department. Not to speak of the unjustifiable position of the system itself, the Political Department, through the abuse of power, has almost totally wrecked the morale of the troops . . . I have talked with many an intelligent man in the services . . . Their reaction toward the activities of the Political Department has reached such a point that they cannot be worse. Some even went so far as to say "If fight we must one day, we shall have to kill the agents of the Political Department first." If we want to employ these troops just for the purpose of giving reviews and parades, it may be feasible. If we want to use them to fight for the recovery of the mainland, I cannot help shuddering at the thought!

On the activities of the secret police -- his third point -- the former Governor had this to say:

During my more than three years' administration ... hardly a day passed without some bitter struggle on my part with the secret police. They interfered with free elections. They made numberless illegal arrests. They tortured and they blackmailed . . . the secret police of our country at present, relying on their special backing, have so abused their powers that they have no regard whatever for law. The people are reduced to such a state that they only dare to resent, but not to speak in the open. If this method is used to ensure the positions of some high authorities, it may be understandable. If we desire to secure the full-hearted support of the people . . . this is utterly impossible.

Turning to the absence of any guarantee of individual rights, he wrote:

As the secret police are rampant, so Formosa has become virtually a police state. The liberties of the people are almost totally suppressed. While I was Governor of Formosa I did my utmost to inculcate the principles that arrests cannot be made without sufficient evidences of crimes and searches cannot be conducted without due process of law. But as my powers were limited, even now I can hardly tell how many innocent people were, and have been illegally held and molested. Every time when I think of this, I cannot but feel an ache in my heart.

Commenting on the absence of press freedom be noted that "Papers have been ordered to suspend publication and reporters have been put into custody from time to time." As for Thought Control, Dr. Wu observed:

The establishment of the so-called "anti-Communist and Save-the-Nation Youth Corps" is really taken after the Hitler Youth and Communist Youth [organizations]. Whether the organ operates under the Kuomintang or the Government (this has never been clarified) I am even now too stupid to comprehend. When I was Governor it demanded financial support from the Provincial Government and met with my refusal. Since then how the organ has been financed is a matter which needs serious investigation. Ever since the establishment of the Youth Corps, principals and superintendents of schools have been forced to become its officers and the students its members, and persistent pressure has been applied to the principals and superintendents to make adjustments in the teaching staffs of the schools in order to regiment the thoughts of the students all the more. To have such an evil way to guide our youth will no doubt leave harm to our posterity for a long time to come.

Dr. Wu asked the Assembly to publish his "six points" and his recommendations concerning them, and notified the Generalissimo that he had done so.

Chiang suppressed the document. An outburst of official propaganda accused Wu of dereliction of duty, corruption in office, and treason. Wu responded in a series of letters to Chiang. The first (March 20) included twelve groups of questions, each group designed to illuminate the issues which he had addressed to the Assembly. For example, the former Govemor asked Chiang:

How many secret police organizations are there in our country? What are the limitations on their powers? Who are in charge of them on the surface? Who is it that really controls them behind the scenes?

Ever since March 1, 1950, the date on which Your Excellency was restored to the Presidency, up till now what is the actual number of people who -have been arrested and put into custody by the secret police?

Are there, or not, secret jails and detention houses in Formosa? Can they be open to inspection and investigation?

Have the secret police, or have they not, interfered with elections in Formosa? Have they or have they not made illegal arrests?

Ever since March 1, 1950, how many newspapers have received orders to suspend publication? And how many newspaper reporters have been arrested? What are the facts pertaining to each case and on what legal grounds were the orders given?

Does the Youth Corps operate as a branch of the Government or as a branch of the Kuomintang?

If it is supposed to operate under the Government, then under what Ministry and why is its organic law not passed by the Legislative Yuan? If it is supposed to operate under the Kuomintang, then why is it that Central News Agency reports that its expenses are budgeted in the National Government?

As for Chiang's attempt to discredit Wu with charges of corruption and dereliction of duty over a long period of years, Wu asked why Chiang had made him Mayor of Shanghai (1946-1949) and Governor of Formosa (1949-1953).

Why was I not dismissed? Why must I resign so many times before my resignation was accepted? Why did Your Excellency yourself pay me high praises ... ?

Why did Your Excellency ask one of your most intimate confidants to write to me on November 20th last year, asking me to return to become your Secretary-General?

As late as February 8, 1954, the Generalissimo had sought to persuade Wu to return to Formosa, but on February 7 the former Governor, in exile, had ventured his first public criticism of the regime. He reminded the Generalissimo of these things, and then spoke frankly of his mistrust of Chiang Ching-kuo the heir-apparent. In a letter to Chiang dated March 28 he revealed the heart of the matter.

When I was in Formosa I gave freely my opinions to Your Excellency on many occasions. I shall just narrate two instances here to refresh Your Excellency's memory.

In 1950 ... I chose a leisurely moment of yours to make a serious proposal. I advocated that the Kuomintang should not be supported financially by the Government Treasury, but by contributions from Party members and that ways and means should be found to encourage the growth of an opposition Party so that we might lay a solid foundation for a two-party system in our politics. Your Excellency did neither agree nor disagree. But as events prove later, Your Excellency has assumed exactly the contrary position.

Then in February, 1952 when I wanted to resign in my struggle for the establishment of the rule of law in Formosa, I spoke to Your Excellency these words: "If Your Excellency loves Ching-kuo your son, you must not let him head the secret police. For no matter whether, relying on your backing, he abuses his powers or not, he will become a target of hatred among the people."

At that time, Your Excellency cried repeatedly that you were having a headache and asked me not to speak any more. But after that, Your Excellency has put more trust in Ching-kuo. Not only has he been permitted to control the secret police and the armed forces, but be has also been given control of the Kuomintang and the Youth Corps. Because of such outspoken criticisms, evidently, an attempt on my life was made on April 5, 1953, a few days before my resignation as Governor of Formosa was finally accepted.

After citing instances in which other important critics suffered, Dr. Wu concluded:

I beg to be permitted to draw the following conclusions: (1) For those who make outspoken criticism in Your Excellency's presence, there is a possibility that attempts may be made on their lives; (2.) For those who speak privately against Your Excellency, there is a possibility that their careers may be ruined and their reputations damaged; (3) For those who spoke critically of the Government and Your Excellency prior to their coming into Formosa even though they may have remained dis creetly silent ever after, there is a possibility that they may be arrested by the secret police and held incommunicado without trial . . .

On April 3, 1954, he sent on a letter to Taipei which probably never reached the irascible Generalissimo's eye. He took note of Chiang's public reputation, and then said:

Your Excellency has been known as a great and determined Anti-Communist, despite all reverses and disasters ...

But the trouble with Your Excellency is your own selfishness. When we were on the mainland you had regard only for your personal political power. In Formosa, after the situation over there has become more secure, Your Excellency has become obsessed again with the idea of transmitting the power to your son. Your love of power is greater than your love of the country. And your love for your son is more than your love for the people. Because of this, Your Excellency has pursued the absolutely wrong course of seeking to control the Kuomintang by yourself, control the Government by the Kuomintang, control the Army by the Political Department, and control the people by the secret police. Your Excellency made that mistake once before, and the mainland was lost. How can Your Excellency make the same mistake again to deprive us of the chance of ever recovering the mainland, and, when it comes to worst, of even defending Formosa effectively? . . .

The situation of our country is, indeed, exceedingly grave. While dark clouds threaten from the outside, there is serious dissension and eruption inside. In order to avert this impending crisis, it is imperative that Your Excellency should do something spectacular . . . [by way of genuine reform].

In recent years another great obstacle to any political progress in our nation is Chiang Ching-kuo, Your Excellency's son. I shall not speak any more about what he stands for and what he does, and the bad reactions of the people . . . It is an undisguisable fact that Ching-kuo was trained in Soviet Russia for some fourteen years, and has no understanding whatever of the modem democratic government. In my humble opinion, it is necessary that Your Excellency, in order to reveal your absolute unselfishness, should not allow Ching-kuo to remain any longer in Formosa at this juncture, either staying in the limelight or behind the scenes ... He should not return to Formosa until after the recovery of the mainland . . . Your Excellency may [then] become cleared of any charge . . . that you entertain any ulterior motive of setting up a dynasty.

P.S.
Reference link and this link
K.C. Wu English bio: 
K. C. Wu Chinese bio:
吴国桢（1903—1985）字峙元，湖北建始人，生于1903年10月21日。幼时天资聪慧，三岁读私塾，《三字经》能倒背如流，乡人称为“神童”。吴六岁随母到北京与父亲团聚，并定居北京。吴国桢读完小学刚十岁，就进了条件极好的天津名校南开中学。他是学校年龄最小的学生，读书用功，校长张伯苓很欣赏他。在南开中学时，吴国桢和周恩来、张道藩、杜建时、段茂澜等同窗。周恩来长他五岁，因志趣相投两人情谊最深，另有一个同学李福景，三人朝夕过从，别的同学称他们为“三剑客”，他们义结金兰。从南开中学毕业后，吴国桢考进清华大学，成绩常名列前茅。
　　1921年毕业于北京清华大学，1923年毕业于美国格林内尔大学，次年获得美国普林斯顿大学硕士学位，继而又获得该校博士学位。就在他读普大时，北洋政府执政、皖系军阀段祺瑞派亲信陆军次长徐树铮到欧美考察。为延揽人才，徐树铮离英赴美前，出了个“何种政治体制适合中国”的问题，让驻美公使交给留美学政治、经济、法律三门课的学生回答。吴国桢应征就政治方面撰写一篇论文，徐树铮看后极为赞赏，认为人才难得。一九二六年，吴国桢的博士论文《中国古代的政治理论》获得评审委员会通过并获得政治学博士学位。
　　1927年回国，先在上海吴淞的国立政治大学教了半年书。接着到国民政府外交部特派江苏交涉员公署任秘书兼交际科科长。1928年任汉口烟酒事务局局长、土地局局长，不久又改任财政局局长、国民政府外交部秘书、外交部第一司副司长。1931年春，吴国桢与黄卓群（汉阳铁厂厂长黄金涛的千金）新婚不久，湖北省政府主席何成浚又委吴国桢为省政府委员兼财政厅厅长。
　　1932年5月11日，29岁的吴国桢被蒋介石委为湖北省政府委员兼汉口市市长。吴国桢在汉口长达6年，民国时期在汉口任市长最长的当推他。吴国桢在汉口市长任内，十分重视市政的兴革。如中山公园的建设，汉口防洪抢险等。时在汉口大水灾之后，市政建设百废待兴、物价上涨、人民生活痛苦，吴上任后改善经济，稳定人民生活，继续完成张公堤堤身加高加固工程、中山公园整修和扩建工程、沿江马路工程等。在市政经费困难条件下，集资在汉口水厂附近建立了一所女子职业学校(后改为市二女中，今为十七中学)，一所完全小学(定名九小，今为六渡桥小学)。加强督学制度，举办中、小学生各项学科比赛。吴国祯在市长任期内是有几分硬气的。当时湖北省会(武昌)公安局长蔡孟坚按照省主席杨永泰的办法，推行保甲制度，吴自巍然不动。1938年10月24日，汉口沦陷，到重庆就立刻上任担任国防最高委员会政务处长。
　　在国防最高委员会任职仅九个月，吴又奉命于危难之间，1939年12月出任重庆市市长，当时作为军事指挥中心的陪都重庆，日寇的飞机多次临空轰炸。吴国桢走马上任，立即疏散人口，清理废墟﹔整顿民防，修防空洞，一切按部就班进行。每次轰炸过后，吴国桢就外出视察。不过，百密总有一疏。1941年6月5日，日机分批多次来轰炸，时间极长。校场口地下大隧道的洞口被堵塞，秩序大乱，1200余人因窒息或相互践踏而死。消息传出，舆论大哗，蒋介石大为震怒，专职的防空副司令胡伯翰撤职查办，吴国桢也引咎辞职。
　　1942年12月交卸重庆市长，改任外交部政务次长。外交部长是宋子文，因他在美国的时间多，实际上吴等于代部长。吴国桢进外交部没有带一个私人，尊重外交部原有的传统，待人谦虚，善待僚属，因此口碑很好。他主持的外交工作也很出色。1943年1月南京国民政府与美国签订《中美条约》，美国交还在华租界并废除了一系列在华特权，同月，宋子文同英国政府代表在重庆签订《中英新约》，废除了英国在华享有的特权，但英拒绝交还香港和九龙。吴国桢谈判有功，蒋奖给他一枚勋章。
　　1945年8月27日，吴继王世杰任国民党中央宣传部长，蒋把他调来打算在即将开始的国共高级会谈中发挥作用。因为周恩来将是中共的主要代表，而周曾是吴的同学与好友。在后来的国共谈判中，事实上吴国桢没有直接参予，国民党方代表是王世杰、张群、张治中、邵力子四人﹔中共方代表是周恩来、王若飞等。吴国桢只管会谈新闻的发布。不过蒋介石与毛泽东的几次会晤，吴国桢都在场。
　　1945年9月17日，蒋与毛在重庆山洞林园会晤时，美国《生活》杂志记者曾摄下这一珍贵的历史镜头，后排右起第一人即是吴国桢。二十世纪八十年代，吴在美国曾向人讲到他对毛与蒋两人的评价。他说：“毛蒋之间，论才，毛大于蒋”。
抗战胜利后，1946年5月，任上海特别市市长。1948年8月，蒋经国以经济督导员身份，赴沪“打老虎”。吴国祯从经济观点着眼，认为用高压的政治手段，无法解决经济问题，抵制蒋经国的“经济改革”，两人产生龃龉。
1949年，大陆临近全面解放，赴台湾任“行政院”政务委员。蒋介石在台湾设置国民党总裁办公室，吴国祯为设计委员。7月，蒋介石应菲律宾总统的邀请，飞赴菲律宾，参加“碧瑶会议”，吴为蒋随员。
　　1949年12月，陈诚辞台湾省主席取，吴国祯接任台湾省主席兼保安司令。1953年4月，吴辞台湾省政府主席职务，留任陈诚内阁政务委员。5月，请假离台湾飞美。以后，蒋介石请人致书吴氏。嘱他回台担任总统府秘书长职务，吴以“政府年来措施，并不与祯之一贯主张相同”，函复拒绝。
　　1954年，吴在美国纽约《民气日报》及芝加哥“WNG电视台”对记者发表谈话，指出台湾国民党一党专权，违反民主法治精神等问题，台湾当局极为不安，明令撤除吴国祯行政院政务委员职务，并经国民党中央改造委员会决议，开除吴国祯党籍。
　　吴初抵美国，任《芝加哥论坛报》远东版编辑两年。1965年，迁居乔治亚州萨凡纳市，应聘为州立阿姆斯壮大学史学教授，晚年致力于中国历史与政治之研究，整理从政史料，并有英文著作问世。1985年6月6日，因病在美国萨凡纳市去世，年82岁。
　　吴国桢的人生道路复杂多变，瑰奇独异，研究现代史少不了研究他，因为在中国现代政坛，他是诸多重大政治事件的当事人和见证人。