First - I never said that USA is good or did nothing bad. Second - what I was saying is exactly what you have said - world is not black and white, there is lots of grades in between. And in such fine grained world USA is higher (whiter) than Russia, China and Iran, and by a lot.

Now to your direct question - USA did a lot of bad stuff and nobody denies it, they did bad stuff in 20th century and in 21st. But again - in comparison China, Russia and Iran are much worse. We can't deny punishment for a killer because of bad childhood, at best we can find killer's offender and punish him too accordingly. Same with USA - they should be held accountable, but only for their own actions, same as other countries.