I'm doubtful that this is really the best way to put it.
The US escalated it's involvement until the early 1970's when via strategic bombing of the North (which the US was unwilling to do previously), decisively destroyed the North Vietnamese ability to fight.
Then, the Americans left.
A couple of years later, the North Vietnamese rehabilitated their forces, and invaded the South.
The reality is such different perspective than 'North Vietnam Won' to the point wherein it's basically almost misinformation to just state it like that.
Finally, the tactical and strategic advantage of the US bombing with Nixon was enormous. The US could have feasibly stayed for a long time - after shedding their fears of 'Bombing the North' and just 'doing it', they finally gained the 'obvious advantage' that a major power should have had.
But Nixon ran on a platform of 'Getting out of Vietnam', and the folks back home lost interest in a miasma of populism.
I think those nuances are important, because I think it demonstrates how tactics, politics and populism fuelled the outcome.
The lessons of 'Fight to Win Only' and 'A long grinding war will turn your population against you' are straight out of the Art of War.
Those lessons informed the 1st US invasion of Iraq (and 2cnd), which was led by Vietnam vets. 'Overwhelming Force and Boots on the Ground to Unambiguously Overwhelm Enemy Forces', though the 2cnd occupation didn't go quite as well.
Finally, literally one day after Barack Obama ordered the last US units out of Baghdad, then Iraqi PM Malaki ordered a purge of Sunnis from his party and government. The Sunni Tribes, in fear of their lives from the then-emboldened Shia dominated Iraqi Army ... invited ISIS in. This very well could have been avoided by keeping a few units, neatly tucked away 'behind the wire' in Baghdad - just enough ongoing oversight and leverage to keep people like Malaki from self-destructing. It would have been better in hindsight to take a longer view of that situation as well.
It's hard to say if there is a direct parallel with Vietnam but it kind of looks like that.