I see these Vietnam comparisons all the time and let me just point out that the US didn't "lose" the war, they pulled out 2 years before it ended and ceased all major military actions. Watergate prevented Nixon from enforcing the Paris Peace Accords (Jan 15 1973) and Ford couldn't veto the Foreign Assistance Act (December 1974) which cut off all funding to South Vietnam.
In order to lose you actually have to be there laying down your weapons and fulfilling conditions as set by the victor at the time of surrender (April 30 1975). Other than the marines who were helping evac civilians from the embassy, and others like those killed during the Mayagüez incident the US really had no major part in the downfall of Saigon or the democratic regime that was vying for power.
Perhaps in the US they use Vietnam as some sort of life lesson to teach children I'm not sure, but "lose" is not a part of the history of US involvement, it never was. Vietnam was friend A helping friend B who was being bullied, but then friend A had to go home after school so he couldn't be there at the last hour when the bully's surrounded friend B. Friend B got beat up, friend A was home eating supper.
All Vietnam is used for in the U.S. is an anti-War beacon. It's hardly taught
True we didn't lose, in fact comparing casualties we were winning, but the fact of the matter is that we never won. And that's the key. The Vietnam War effort was shot to pieces by the hippie movement and the spawn of the liberal media in the U.S. There was no support, we never sent enough troops to solidify defense and we never moved to finish the conflict because we were afraid of what the rest of the world thought. It was stupid, we were there because someone believed in the domino effect (one free country's fall into communism will result in the rest of the world falling into communsim, didn't happen obviously) and because France was too stupid to beat the VC when the beatin' was good. There's this whole post WWII culture, of not invading another country, that has been crippling all military efforts since that time.
Truth is that the U.S. needs to decide if it wants to try to fix fucked up countries or if it wants to just close its borders and hope nothing comes its way. What we're attempting to do now is both, we want to stop global problems but we also don't want to commit to them because we can't stand to see our own troops die.
I myself am an expansionist and I want to see the world come into American hands, but the rest of you Americans need to figure out what it is you want.
P.S. I know I didn't address Terrorism, maybe later