There is no way the US could have won the war in Vietnam without using nuclear weapons, commiting genocide on a massive scale, invading and conquering North Vietnam, or basically occupying South Vietnam forever.
80% of the Vietnamese people supported the communists. And this fact doesn't change just because the US uses even more violent tactics and commits mass murder on an even larger scale than they allready did in OTL.
Cutting of the Ho-Chi-Minh trail basically means occupying Cambodia and Laos. And it has to be noted that the King of Cambodia allowed North Vietnamese forces to pass through the country (North Vietnam never invaded Cambodia). As for Laos, the NVA occupied the nations' eastern territories with the help of local guerilos. And, as was allready noted by other people on this thread, occupying Cambodia and Laos will cause even more people in Indochina (if that's even possible) to hate the US.
South Vietnam was an artifical pupet state, a state that never had popular support and was kept alive only through american arms. And the more violence the US uses, the more vigorously the people will hate them.
Would you mind providing a source? Furthermore, as a german, I'm very hesitant to use the word "concentration camp" in another context than that if the Third Reich. Equating Vietnamese labour camps with Treblinka or Auschwitz is simply wrong.
That's dehumanizing. Every sane human beeing has to agree that "just killing Vietnamese people untill there are non left to fight back" is no solution.
It's also basically the american version of the Dolchstoßlegende. What many americans fail to realize, is that the US didn't loose because "weak politicians", "leftist media", or "stupid hippies that didn't understand the Domino Effect" ostensibly stabbed them in the back. They lost because they were foreign occupiers that oppressed a free born people with utmost brutality.