I heartily agree with the need for the history of that period to be told straight. But calling Vietnam America's first defeat is ceding to America's enemies rhetorical and intellectual territory which should be defended or retaken.
The enemies of America like to portary campaigns as separate wars so that when a campaign goes badly they can unite all who oppose war generically, all who oppose the conduct of the particular campaign, all who oppose America's particular goals, and all who hate America in a grand coalition. That's what they did with Vietnam and that's what they're trying to do with Iraq.
Neither was or is a war, each was or is a campaign in a larger war. WW III (a.k.a. the Cold War) in the case of Vietnam, and WW IV (a.k.a. the War on Terror) in the case of Iraq. America has lost campaigns in wars it has won--the disasterous campaign which led to the terrible winter at Valley Forge and the mid-Atlantic campaign of the War of 1812 when the British burned the White House spring to mind.
For the history to be written right, Vietnam must be seen as a campaign in the ultimately successful Cold War which was lost because of the domestic forces you decry.
We still need to have a Cold War victory parade with Vietnam and Korea veterans marching front and center.
I agree with all of your very perceptive points.