I assume by hogwash you mean some sort of fantastic aromatherapeutic, citrus and cinnamon concoction for bathing magic pigs.
Even with the USA fighting for Vietnam the communists went on to topple Laos and Cambodia. If Vietnam had been uncontested give me a couple of reasons why Thailand, Burma, and Malaysia would have survived?
When you can think of reasons why the rest of Southeast Asia would have survived, can you then explain why Northeast india - a place still suffering a communist insurgency - would have been OK. I sure as hell can't, so I'll be very impressed if you can.
Firstly, Vietnam is a tremendous success story for the communist takeover, Ho Chi Minh is second in fame only to Che Guevara, who also happens to be the most well known individual in the world according to several surveys.
The greatest military in the world sent home beaten, people demonstrating in the street all over the west for the rigth of the Vietnamese to take his fate into his own hands. Were a second communist insurgency to follow the withdrawal from Vietnam, the US would have been completely powerless to stop it.
Where exactly is the deterrant here ?
Secondly, the way to lessen the chance of two superpowers figthing a war too terrible to imagine is to fight less satelite wars, not more.