What I mean by this is what if instead of the Iraqi conflict of 1991, which I think was the next major conflict that the United States was directly involved in after Vietnam, something... rather different happened.
Instead, what if turned into another guerrilla campaign. Another grinding attrition war. Now, what country would fulfill this? I don't know, however there are candidates, like Iran possibly.
Point is, what's the cultural impact? What would happen if the next war was like Vietnam all over again? Keep in mind, I mean in the sense of a never ending attrition war with guerrillas who won't give up, and the drainage of morale. Yes, this needs to be on a greater scale than the 2nd Iraqi War.