General Discussion

Japanese internment during WW2.
The butchering of the Filipinos during the Filipino-American War after the Spanish American War, including the use of concentration camps.
ICE concentration camps
Mass killings of civilians during the 1st and 2nd Caco War in Haiti
Trophy taking of dead Japanese during WW2. FDR was even mailed an ear of one as a trophy
Mass rape during the Battle of Okinawa
My Lai, Operation Speedy Express during Vietnam
No Gun Ri during Korea

MANY, MANY more.

All documented cases that American combat troops were participants in crimes against humanity.

Just a weak Google or Wikipedia search stating "American war crimes" and all of this is documented and verifiable.

A main psychological objective in war is to dehumanize the "enemy," making it easier to kill and abuse them. The Enemy aren't people.