The US was had troops in South Vietnam since it was founded. It was a rump French puppet state with incredibly corrupt catholic government that was persecuting the Buddhist minorities. The north was made up of the national forces that kicked the French out. They had every right to overthrow the southern government.

This isnt russian troll position. Americans were saying this enmasse the start of the Vietnam war. American protestors died to stop that war. Draftees killed their officers frequently over it. Read anything about it.