The Onion

Well, the US stayed out of the conflict until after the Battle of Stalingrad. The US was hoping the Nazis would destroy the USSR, which it looked like they might, but once the Russians started pushing back west the US realized they couldn't allow Russia to win the war. So they teamed up with the UK, invaded France and cleaned up the western front and told their people that it was actually the US/UK that won the war when the most sacrifices were made, and the actual turning point was achieved by the USSR.

Consequently fascism wasn't completely eradicated, it was absorbed into the western consensus as the virulent anticommunism of the Nazis was quite valuable. Several high ranking Nazi generals were recruited to form NATO, and rocket scientists were also brought into the fold. The vast majority of companies, and their executives who cooperated with and were fervent enablers of the Nazis, received no punishment at all; as punishing business dealings with the Nazis would implicate american businesses such as IBM whose second largest customer was Nazi Germany (the first being the USA). The few executives tried at Nuremburg received diminished sentences.