You think we should have supported the communists in the north?
Exactly - from the very FIRST overtures that Ho Chi Minh made to the US. There was no “North” and “South” when we should have made the better decision. Those came about because of our poor knee-jerk reactions.
The ‘horrors of communism’ that we were supposedly trying to contain and destroy were the effects of our own earlier decisions, trying to support the stupidity of French colonial actions and related political corruption.
For all the talk about Constitution and Declaration of Independence, in foreign relations the US really hasn’t walked that walk in a very long time.