Don’t think Iraq is the same as Vietnam version 2. For one, lot more of us died in Vietnam. Second, in the end, Vietnam paved an independent path, and the domino theory was discredited. In contrast, in Iraq, it is the big domino that we gave on a platter to Iraq.
Try telling that to the dominoes in Laos, Cambodia, the "independent" boat people who fled HoChiMinh City by the hundreds of thousands, and the ten or so other countries that went communist during the next four years of the hapless Carter administration, once they realized that the US was no longer serious about containment.