They were defeated!
There is no end to the US's military power. They can go on for decades and decades longer. They didn't achieve their goal, they were defeated by one of the greatest military strategists in history, and the will of the Vietnamese people to resist.
Its insanely weird to deny the victories of decades of struggle by Vietnamese people and make it about the heroism of white kids back home. It has all the qualities of white savior complex.
If popularity determined which wars happen we wouldn't have ever been in Iraq in the first place. Our protests against Iraq were larger than the 70s protests, actually, and they were simply blotted out of the news. We're still in Iraq and Syria, which have been pummeled and turned to dust. Had Vietnamese resistance not been so enduring, the US wouldn't have left there either.
They remain throughout the pacific.