Actually, war would take a lot more if the Americans hadn't helped the Soviets. Moscow could fall, but they would retreat even more and more people would die. But, as they got lots of supplies from USA, war was shortened.
To check it, just take this facts:
1 - At some time, the Soviets had 555 divisions against the Germans
2 - They used lots of American equipment, but their best weapons were Soviet(T-34, JSIII,
et cetera)
3 - The Germans were trying to get everything they could against the Soviets
4 - Most weird tactics and weapons were used against sovietics(Mistral...)
5 - The Eastern Front was falling, if not quickly, constantly.
6 - Ardennes was a last-ditch operation, as Hitler hoped to get a cease-fire with the Western Allies to fight the Soviets.
(God, we will end at the OTZ
)