I personally was against it for the reasons that #1: it was never declared, so technically non-sanctioned; and #2: there was too much division in the U.S. at that time to go full steam ahead and fight a real war instead of one with one's hand tied behind one's back, such as the flying of 20 planes with one bomb each during missions, which truly did happen. I do, however, think that there was some truth to the "domino theory".
As far as the outcome, the U.S. 's image as a policeman was tarnished and it was the beginning of the movement, now reaching top-speed, of dissing the States, a phenomenon you Brits witness in your own history in Khartoum, Afghanistan, the Dardanelles and India (relax- I'm on your side).
I personally would not want to do it again - I would have used "spheres" of influence where embargoes were in place, much as the way in which the States have dealt with Cuba.
I think it has resulted in a reluctance on the part of U.S. citizens and residents to get involved in much warfare or sanction/approve of it. I think it's quite possible that if Adolph Hitler were alive now instead of in the 20th century that we as a nation would turn a blind eye and hide under the sheets, much the same as in the fable of the boy who cried wolf who had his guts eaten while everybody ignored him.
That's why war can never be about popularity.