I think the economic gap between the US and USSR in the late 1940s had more to do with the czars and distance from northwestern Europe than the Nazis or Communists. Russia was very far behind the industrial countries before the revolution, and remained so thereafter.

If anything, the Soviet modernization efforts accelerated what would have been possible under the czars. Because of Soviet growth during the Great Depression, communism was seen by many in the industrial world as a viable alternative during the 1930s.

Command economies are great at catching up (just ask Park Chung-hee) and terrible at expanding the economic frontier. Not a fan of command economies by any means, but history is more nuanced.