Japan basically gets away with that by claiming to be the natural successor for the "Mandate of Heaven" after China turned into two Republics (if you count the now Taiwan-based PRC) and a Tibetan Theocracy. Thus legitimizing their rule over Korea and Manchuria as protecting the traditional nobilities of Korea and Manchuria from the prying hands of Kuomintang-headed Republican dictatorship that controls the biggest part of broken China. Add to that with how Kuomintang basically alienated everyone with claiming not only Manchuria and Tibet (which is quite historically understandable), but also Korea, Mongolia, Uighoristan, and even parts of former French Indochina... There are few incentives for anyone to support the independence of both Korea and Manchuria (because those "Korean and Manchurian Nationalists" often said that their countries were rightful parts of China).True, nowadays people do point out about Japanese being hypocrites with their "Not-Colonies" of Choson/Korea and Manshukoku/Manchuria. Technically those two are indeed not colonies, but Vassal Kingdoms of the Japanese Emperor (The Joseon and Aisin-Gioro are still their regional rulers), but most of their population and culture ended up being Japanized anyway. But that was how Realpolitik happened.
You shouldn't be surprised at why the USA supported the Nazis, even now, just look at how they basically forced all the Jews living there to either accept Christianity or get expelled with all their properties confiscated during the peak of "Christian Nation" movement in early 20th Century. Yes, the Nazis are overt racial supremacists while the Evangelicals are more about religious supremacists, they have a lot of overlap. Contrast with how secular Britain has become now, and you have the answer.The issue of Nazi War Criminals fleeing to the United States can primarily be chalked up to the influence of the German-American communities more distasteful elements including the very offensive politics of the wealthy Dietrichs. While yes, those men should've faced justice the fact of the matter was and is that the bad blood between Washington and the Commonwealth made extradition a no-sell.
I don't it's particularly fair to paint the US as an utter sponsor of dictatorships and tyrants, however. the Philipines and Cuba are rather prosperous democracies, and Britain has had its long bloody history of sporting strongmen and dictators in the Middleast, and that's without mentioning the "methods" employed by Commonwealth forces in the "Emergencies" in Kenya, and Aden, or the Bush wars in Rhodesia and South Africa.