Yes, especially seeing as how the US had supported communists in the past, for example the Khmer Rouge. Apart from using French communists as political proxies (As you're probably aware Ho Chi Minh was a founding member of the French Communist Party) I don't think there was any way for the US to both involve itself in Vietnam and maintain full control. And even then it wouldn't have been easy to control the Frenchies. This isn't strictly true. Apart from nuclear arms the historical record shows there were few practical limits to US actions. The US bombed neutral countries like Cambodia, flattened North Vietnamese cities, poisoned rainforests and water supplies, held civilian populations captive in giant enclosures or simply wiped them out etc. The limits were purely those of firepower rather than any political restraint. It was only with nuclear arms that Vietnam could have been completely cleansed of opposition to the South Vietnamese President; perhaps had he been replaced with someone less corrupt there would have been fewer problems, but apparently this was not possible at the time. In any event I think we'll have to wait another 20 years or so for the 50-year sealed documents to come out before we can make any definitive statements on failures and successes in Vietnam. There's just too many variables to work it out now.