Well in South Vietnam we lost, can’t really blame us for abandoning a lost battlefield. But we do have a history of a firm handshake and walking out the door once we’ve gotten what we want out of another country. The US is definitely not the kind of guy who makes breakfast the next morning. And I think that’s a good discussion to have right now while we’re in Iraq, everybody whose complaining we should flee Iraq (and Afghanistan) is basically saying we should do now what we did in 1989, and the need to be reminded of just how well that worked.
As for 'Nam, we won that when the NVA sued for peace after operation Linebacker II, but the (D) led 1975 congress abandoned it to the commies... with disastrous results.