And the reason for the politics back home was because of the confusion. It was supposed to be a war of liberation, which obviously implies collaboration with the locals, hearts and minds campaigns, etc.
It should have been said from the start that the war was not about the locals, but fiighting for US interests. That way, people would have known from the start that heavy military force would be accepted. The misison needs to be clearly defined.
Look at WWII. It was clear and simple... defeat the Nazis. For a military operation, that's how simple the mission must be. None of this liberation half military half diplomatic stuff. it must be made clear that you're going to destroy something.
"fiighting for US interests"
And what would they be? I'm shooting from memory but I think the major selling point was the 'domino theory' and the need to stop communiism during the cold war that was still in effect.
"collaboration with the locals, hearts and minds campaigns, etc."
There was all that. Some worked, some didn't. Much of the US Army (and even some Marines) in Vietnam was comprised of draftees. That in inself is enough for a lot to have not worked. The difference between now and then is the difference between living on earth and living on another planet. That's how different things are today.