America won the Vietnam war. Here's why:
>Mission objective: stop the communists insurgencies from taking over South Vietnam
>Mission accomplished: After the Tet Offensive the Viet Cong was gutted and in no way capable of taking over the country
>Next: The USAF bombs the shit out of Hanoi and forces them to sign a treaty respecting South Vietnam's sovereignty
>America exits instead of keeping forces there forever like in Korea
>2 years later North Korea violates the treaty they wrote and takes over the South, but by that point America did not care and had stopped supplying the South
See? They never intended to invade North Vietnam or to stay there forever. They achieved what they set out to do, hence victory.

>b-but North Vietnam took over the South LATER
Yeah and LATER a McDonald's flag flies over Hanoi. We are talking about the actual war.