Cal though is right on when he said that Americans did not die in vain. We presented our culture, warts and all, and saw the generality of Vietnamese adopt it as part of their own. That is why the nominal victors can never have the kind of regime they thought they were getting.
In addition, without our valor there could never have been a Reagan Presidency, the USSR would still be in business, ad infinium, ad nauseum. Me? If I had not gone and done as I did, I would have no self-respect at all. So would I do it again? Don't ask silly questions.