“Stalin never would have left Eastern Europe just because you asked him to do so.”
Stalin halted his armies after the Soviet territory had been cleared, then asked the Western Allies what incentive he had to continue a war that had already cost so many Russian lives. In order to keep the pressure up on the Eastern Front while the allies came in from the west, they gave him Eastern Europe.
The Soviet Union was spent by that time, anyway; most of the ethnic Russians for that generation were killed, and replaced by Far Eastern minorities; they even had women in combat roles (the effect of that loss of life can be seen even today). The move into Eastern Europe was behind a rolling artillery barrage, as they had more shells than men.
Americans didn’t go to war to liberate Eastern Europe/Poland; we probably had the least reason of any combatants to fight in Europe.
That's an interesting take on the situation. From what I'd read, Stalin wanted Eastern Europe as a buffer region between him and the West. Stalin didn't want any more surprise attacks into Soviet territory like what had happened in 1941. If that were the case, Stalin would have grabbed the region regardless.