Americans knew. At least the ones that gave a shit. There were protests and fights every year over bullshit the government was doing.

Sounds like maybe you didn't know? And once in the military they had their propaganda for you.

You really didn't hear people talking about all the devastation the US brought to do many people for decades? People are still dying to this day in the country that had more bombs dropped on it than used in all of WW2, and the US wasn't even at war with them!