Iraq is like Vietnam for two very basic and simple reasons:
1) As in the 1960's, we are led by a group of geopolitical types who think that the world is a chessboard, with the U.S. as grandmaster chess champion and all the other countries in the world as chesspieces (mostly pawns, others more powerful).
In their view, the job of the U.S. is to move all the pieces around in such a way as to yield the U.S. maximum benefit.
As in a chess game, there is no consideration given to the possibility that any of the individual pieces have any personality, creativity, history or interests of their own (other than their nominal attack capabilities vis a vis each other) much less any important relationships they might have with each other, any or all of which might foil our grand plans.
2) The Iraqis, like the Vietnamese, really hate it when we muck around in their affairs, and will fight us to the death because of it.
That's it; no over-intellecutalizing necessary!