Germany would have shredded the USSR.
The only reason the USSR was able to field big armies was due to American supplied equipment and industrial assistance.
We lost thousands of merchant seaman taking supplies over there.
We trucked stuff up through Persia.
We bombed the crap out of germany from the air, weakening their industry.
We bombed Ploesti Romania on basically suicide raids, disrupting vital petroleum reserves.
We supported the Brits who tossed the Germans out of N. Africa and supported the Yugo resistance of Tito in the Balkans, tying up German resources lie crazy.
Stalin abandoned Moscow ahead of the Germans.
Only when our resources supported his armies did he even stand a chance.
And the brave charges of the Soviet Soldiers were certainly motivated at least in part by the officers who they knew whould shoot them if they came back.
Yes the USSR might have eventually ground down Germany, but it is more likely Stalin would have simply cut a deal with Hitler, as he had before so profitably and as he was apparently seeking secretly to do until nearly the end of the of the war.
Ed