I completely disagree that any of these conflicts other than Vietnam, were lost. They were just inappropriate use of the military power, akin to the Soviet invasion to Afghanistan. Americans never had a big problem of defeating any enemy, problem was what to do next (and Iraq-91 was a victory for exactly that reason: they quickly withdrew and left defeated Saddam to deal with the mess, with Schwartskopf correctly stating that there is no interest for U.S. to 'run the country'). If you see 'victory' as 'Iraq (or Afghanistan) adopting a stable US-style democracy', which apparently was an intent, than this 'war' is not winnable, and there is nothing to blame military for in this fact.
In fact, Soviets had similar problems. They could win wars when they really wanted to, but they similarly set unrealistic, or outright lunatic political objectives which predictably failed. Communism works in Afghanistan no better than democracy.
The Vietnam War being lost is similar to proclaiming that Iraq was lost after the invasion (the occupation time frame). There was no victory basis in either case. Vietnam was a holding pattern, as the US chose not to march north with its full might.
Not to mention, the Vietnam War was a civil war. Would we declare that France lost the Revolutionary War, had the colonies been defeated by Britain? I'm skeptical.
Had the US abandoned South Korea like it did South Vietnam, people would proclaim the Korean War a failure as well. The primary difference between the two, is the US chose to protect South Korea perpetually. Had the US stayed and protected South Vietnam, I think it's very unlikely that war would be regarded as essentially a total failure. It's not very complicated, the US chose to leave because it was exhausted culturally, not because it was defeated militarily.
