Did North Vietnam win the Vietnam War?

Yes, several years after the US pulled out. North Vietnam finally conquered South Vietnam. But they did not defeat the US military! The US in fact destroyed their military, and it took them those several years to rebuild before they were able to defeat the South. In those few years the US pulled out of Vietnam, only leaving forces in some cities, mainly Saigon security forces (which were shown scrambling to leave the city on international news). This is why it looks like the US was running with its tail tucked between its legs, when in fact all major combat units had been gone for some time.