Well that is just it, the wealthy of the US were totally on board with the Nazi. Industrialists like Ford help to bankroll the Nazi Empire by building factories and saying they could keep all the profits. Not to mention IBM developing the number system for the tattoos on Jewish prisoners and helping with the logistics of sending them to the death camps
Hitler didn't even want to kill the Jews at first, he wanted to exile them and sent envoys to see if other countries would take them. When the wealthy of the US found out they went and lobbied against this and stroked more anti-jewish sentiment in Europe to ensure the final solution would happen. Hell, even Hitler said he based the Holocaust after the Native American genocide the US committed.