what? the Soviets were never allied with the Nazis. During the Bolshevics revolution there were crews on German naval ships who were inspired and mutinied against the German imperialists in WWI.
The U.S. never became involved in WWII(with the exception of some Americans, on their own initiative, for the most part, volunteering to help with the British against the Nazis) until the Japanese imperialists bombed Pearl Harbor.
...although the U.S. did help Mao by providing the imperialists in China with equipment the Red Army captured in the civil war.