It's funny that you wrote a short history of the Vietnam War and didn't mention the bungling French colonists that created the whole situation in the 1940s and 50s. After the USA pulled its forces that were protecting South Vietnam from the invasion by North Vietnam out of the country in 1973, the North Vietnamese Army rolled south with Soviet tanks and jets and defeated the forces of the Republic of South Vietnam. The Viet Cong, at least the few that were still alive after they had been used as cannon fodder by the NVA during the 1968 Tet Offensive, was dissolved shortly thereafter. They had no say in administering the united Vietnam, and had basically fought and died for nothing. The North Vietnamese established the Marxist Leninist single party totalitarian police state that rules the country to this day. Hooray for that I guess.

The People's Republic of China's invasion of Vietnem in 1979 is probably a closer parallel. The Chinese had their ass handed to them by the Vietnamese. Other than having some outposts overrun, the USA never lost a battle.