While the estimates of total casualties vary quite a bit, an enormous number of people were killed in Vietnam. It was basically a genocide. Even if you believe

While the estimates of total casualties vary quite a bit, an enormous number of people were killed in Vietnam. It was basically a genocide. Even if you believe in the domino theory (personally think that was nonsense) there's no real scenario where the war could have been a net positive. The US put that corrupt local government in power by the way.