Germany had half their army fighting Stalin on D-Day, so if they had not been pinned down in the east, Hitler could have made the Allied invasion much more costly. But thats just ‘what-iffing’ on my part.
We were also busy fighting the Japs pretty much on our own, so that Japan had no desire to mess with the Soviets during that time.
Had Japan been freed up to attack the Soviets in Siberia, that would have definitely been a problem for the Soviets.