I thought taking a hardline anti-Vietnam war stance in 2023 would be a slam-dunk but apparently not.
If the right choices had been made in the 1940s and early 1950s, it wouldn't have been that hard to turn Vietnam into an East Asian equivalent of Yugoslavia, if not an actual US ally
Wars are politics and end only with a stable political settlement; without that, they can go on indefinitely - such as in Afghanistan recently.
Like Afghanistan, there was nobody in Vietnam that could run the country, politically, except the North Vietnamese. All the US could do was build someone else's capability, which wasn't working (in Vietname or Afghanistan) or fight indefinitely.