>>18142499 (OP)
The soviets actually were necessary to get Nazis to attack, Stalin and Hitler agreed in early 1939 to start the war and soviets supplied the Nazis with necessary equipment.
America in turn funded the soviets via oil and America was permissive of soviet's taking over the Baltic and everything else soviet's did.
America bears ultimate responsibility for everything that happened by funding the soviets, supporting partisans during the war that did all the crimes, and keeping the soviets in the war when they would have otherwise collapsed due to bureaucracy.