Both the USSR and USA enjoyed the luxury of surviving World War II with their territories and economies largely intact
You are terribly wrong about this. The western part of the USSR was occupied by nazi Germany and most of the industrial facilities of the USSR were located in the west (Ukraine and Belarus) before the war. Those territories suffered from a lot of destruction and millions of people in the USSR died during the war (around 20 million). Saying that the USSR "enjoyed the luxury of surviving WWII" is simply stupid and ignorant.
The USSR didn't "enjoy" anything.
Russia continued to construct enormous quantities of tanks late into World War II.
Russia's factories, infrastructure and residential sectors had not been hit as hard as other countries. Which allowed their wartime production to thrive.
Comparing the devastation of nagasaki, hiroshima or UK cities bombed consecutively over long periods of time. Russia got off easy in comparison.
Russia and the united states were also in the best position to assimilate technology from nazi germany which was the reason behind those two nations being the main players in the space race.
Your 20 million statistic is likely correlated with russia's great famine rather than World War II btw.