Liberals tend to be real nit-picky about American crimes, and turn a blind eye towards those of the other guys. But I think this is a reaction to the usual Conservative position that we are saints (the current term is "American exceptionalism") and everyone else is an asshole. The truth has to be somewhere in between, unless you really believe some people's DNA is superior to others, and that further, the good DNA tends to collect in some counties, and the bad DNA in others.

Nations, just like people, tend to behave in such a way as to promote their interests and advance their own fortunes, and they tend to interpret the world in such a way that they sincerely and honestly believe that what is best for them must be best for everybody else. The fact that others don't see the world the same way is invariably perceived as hostility and evil.

People are pretty much the same everywhere, and although human cultures do vary widely, and they are all dealt a different hand by history, I think all of them are equally capable of both good and bad. The rest is all propaganda. Have you noticed how the English are always portrayed in the movies as civilized and decent, (except in movies about the American Revolution, where they are invariably depicted as complete assholes)? But ask the Scots, Welsh and Irish how they feel about the English...

The Nazis and Imperial Japanese were brutal Fascist cultures that needed to be exterminated, but we did so by allying ourselves with brutal Stalinism to do it, not to mention the Imperialist countries of Europe who owned half the world and operated it as a profitable colonial sweatshop business at the expense of the native inhabitants. And our treatment of Negroes, although nowhere near as vicious as the Nazi treatment of Jews, still was pretty foul until fairly recently, and even today, still has a long way to go.

As hank points out below, "its all relative". Nothing is all good or all bad all the time. But sometimes, we do have to pick sides, whether we like it or not.