1a - Is it true that US high command thought that air power could win the war in Vietnam almost by itself?
1b - In such a short period of time?
No, and no.
The US has, at least since WWI, been a global player. However, the population of the US is extremely isolationist in its views. As long as something is happening “over there”, the general population of the US doesn’t want to get involved. The US was quick to aid Britain in WWII with supplies and munitions, but was very reluctant to enter the war until Pearl Harbor forced us into it.
In Vietnam, the same isolationist attitude was there. People didn’t want to get involved in some war in some country that a lot of people couldn’t find on a map. Kennedy followed Truman’s policies on the cold war though, and there was a fear that if we didn’t get involved in Vietnam then communism would spread throughout Asia and we’d have a big problem on our hands. Kennedy didn’t just jump into the war though. Instead, there was a slow buildup of our involvement. We didn’t jump in with an air war plan. The plan was to let the Vietnamese do the bulk of the fighting. We would help just enough to make sure that the “evil commies” didn’t win.
That strategy worked about as poorly as you’d expect, and Johnson escalated things quite a bit after the Gulf of Tonkin. At no point did we jump in thinking that this would be a quick war. The strategy throughout the war was that we would keep escalating until they gave up, and both Kennedy and Johnson severely underestimated the will of the North Vietnamese.
2a - Would you agree or disagree that US military doctrine has focused on winning through air power?
2b - Would you say that there have been points in time where the prevailing attitude is that air power, almost by itself. can win wars?
I would disagree. The US has a definite focus on air power and achieving air superiority as a major part of its strategy. In Vietnam, they didn’t think that they needed to hold land with ground troops as they had in earlier wars, although they still thought attacking with ground troops was definitely necessary. That strategy didn’t work, and one of the clear lessons of Vietnam was that you need to hold ground in order to win.
The first Gulf War started out with a very large air war phase, and that worked well. It was followed by a ground phase though, and that ground phase had always been a part of the plan. The second Gulf War was focused from the start as a ground war, mostly to save money.
3 - If these are true, what are the historical origins of this attitude? Is the success of air power in the Pacific?
WWII, Korea, Vietnam, pretty much every war has proven the benefits of achieving air superiority. Once you have air superiority, you can bomb the other country at will and there’s not much they can do about it. You can’t actually win without troops on the ground, though. Every war we were in during the 20th century proved that over and over.