You mean revisionist "historians", who were part of the "Hate America First" crowd during the War, and were out there actively protesting it. Not exactly a credible source.
As far as them teaching us a "lesson" about guerilla warfare, exactly how do your square that with the fact that we beat them unmercifully, for over a decade, and the casualty count in combat was over 100 to 1.
If you think that losing 100 of your fellow Commies to one red blooded American, and then having to sue for peace qualifies as a victory, you really should seek professional psychological counseling ASAP.