Fighting an essentially defensive war is a losing proposition to begin with in most instances. Korea being the best counter to that argument, but even then the offensive above the 38th parallel and the subsequent Chinese intervention turned it back into a stalemate.
Vietnam was an effort to stop the North from coming South. A defensive war. Really hard to win that kind as it gives the offense all the advantages.
That said, I agree mostly with evalu8ter's:
1. The USAF was obsessed with the "big one" and only grudgingly accepted the Spad, SLUF et al into the inventory when it became obvious that the OrBat was wrong for SEA (when, if ever, will we come to the same opinion...)
2. Basic rules of war were ignored. "Gradualism" seemed a RANDesque construct that had/has little place in the tenets of war; It is difficult to "send messages" whilst bombing a country, particularly when youe refrain from hitting vital infrastructure (Haiphong, Phuc Yen, SAM sites, Dams etc) for fear of widening the war.
3. The VN war was the first "Long Screwdriver" War. To paraphrase, "War is too important to be left to politically motivated individuals"
4. The desire for all branches of the US military to be seen to be important, wary of losing their slice of the pie.
I would also take issue with the Janes synoposis. The rapid defeat of 1975 was hastened by the restrictions imposed upon US Air Power by a anti-war Congress / Senate who prevented Ford from launching strikes to support the SVN state or by providing the required weaponry (as they had to Israel) to stop the NVN Armour (note that the 1971 use of NVN armour had been repelled by TOW missiles, many fired by AH-1s). The ARVN was organised along unit v unit lines, it was just not very good at it.
Vietnam-era ROE were inordinately restrictive as Washington was worried about the press/world opinion not necessarily at winning militarily. A lack of the appropriate munitions - launching sorties with one 500lb'er to keep sortie counts up, thus unit 'effectiveness,' and the like did nothing to help. By the time Washington did wake up to the military facts, it was too late politically.
ROE in Kosovo were inordinately restrictive, but the politicians couldn't handle the heat if there were dead airmen paraded through Pristina or the like.
Don't slip the dogs if you're not going to go all out.
If you aren't, figure out another way to talk to the other side.
If you are, give the word, then step back.
Desert Storm was about right, in my mind.