My highshool spent some time on it. I don't recall it all that well, but basically, it was taught that we went in for poor reasons, and everything went downhill from there. At this time, we were in the Cold War, and The Soviet Union had been picking up satellite countries and leading them into communism (whether this was a good or bad thing for those countries, I have no idea). America was nervous about the rapid spread of communism, and decided to pick its battle in Vietnam.
There was already a faction in Vietnam that wanted independence, so we decided to support and bolster that faction against the rest of the country.
We had superior numbers and technology, but it didn't mean anything due to the nature of the war being mainly guerrilla warfare and the huge home-turf advantage Vietnam had over us. I don't remember the numbers, but I know a significant portion of the deaths and injuries were simply due to the viciousness of the jungle. The war became immensely unpopular back home.
In desperation to turn the tides, generals of America attempted to remove the home-turf advantage by destroying the home turf. Fly-overs with carpet bombs to blast hundreds of acres of jungle. We also used Napalm, which literally melted flesh off of bones from the heat, and Agent Orange, a really nasty neurochemical warfare that caused delusions and stuff.
At this point, even the Vietnamese seeking independence wanted us gone. Loss of support in both Vietnam and in America, with staggering death tolls on either side, and no clear way of winning the war without burning Vietnam to the ground, we retreated.
Since America doesn't like to lose though, I think technically, we've declared a ceasefire, rather than actually surrendering. But being as we ran back across the pond, the war's over, and we lost.
It was taught as a war we had no business fighting. Or at least, we shouldn't have initiated draft, and we shouldn't have resorted to bombing. It should have just been support for the faction, not a full offensive movement. I'm pretty sure it goes down as one of the darkest times in US history.
I'm no historian though. This is just what I recall from my highschool.