Now I'm not exactly sure what the Vietnam war was supposed to achieve, and insofar as it fizzled out we need to define what, exactly, the aim was. I suspect it was pointless and fizzled out due to pointlessness eventually overwhelming the ability of the Americans to fight.
However, if it was to combat communism/the USSR, which is my hazy understanding of the official justification, note communism has largely been expunged as a political ideology. All the communist states failed. The majors (USSR & China) have moved to capitalism. Well, China did. The USSR was removed from the map.
> Those who argue that the United States’ opponents won the war cite the United States’ overall objectives and outcomes. The United States entered Vietnam with the principal purpose of preventing a communist takeover of the region. In that respect, it failed: the two Vietnams were united under a communist banner in July 1976. Neighbouring Laos and Cambodia similarly fell to communists. Furthermore, domestic unrest and the financial cost of war made peace—and troop withdrawals—a necessity, not a choice.
In fairness, it also says that some people think the US won because it won the major battles and inflicted more casualties. That sounds like winning the battle but losing the war, to me.
If your argument is that the Vietnam War failed to achieve its goals, in context I don't see how sustaining the war for a millennium would have helped. The US arguably identified (correctly) that their approach wasn't working and stopped.
They then crushed communism. I don't see an argument that communism is a credible ideology these days. We all know what will happen to any country that makes a serious go of it - the citizens will starve and the economy will collapse. Then they can't spread communist ideology any more because they're broke and humiliated. The defeat was so resounding that the options became liberal capitalism, authoritarian capitalism or irrelevance.
If I hated someone enough that I wanted to bring war to their doorstep, and then decided that wasn't enough, I'd wish communism on them to. So insofar as the US was defeated in Vietnam, they won the war so much that the battle turned out not to need sustaining. I don't think this example shows any sort of survivorship bias, I think it is just a case where the project was achieved quickly.
However, if it was to combat communism/the USSR, which is my hazy understanding of the official justification, note communism has largely been expunged as a political ideology. All the communist states failed. The majors (USSR & China) have moved to capitalism. Well, China did. The USSR was removed from the map.