The Korean War was a folly from beginning to end. The reason North Korea thought itself free to invade South Korea was that the American secretary of state, Dean Acheson, publicly put Korea outside the sphere of America’s interests. Truman changed the American policy only after the attack.
On the other hand, the fact that the USSR’s economic system was absurd doesn’t answer the question whether it was an existential threat to the USA. After all, one could have made a similar argument in Tibet c. 1950: “China’s economic system is absurd, so we have nothing to fear.” What good would that do him now?
I might add that the economic system of the United States is absurd as well.