To add to your points on Iraq, I have always maintained we should never have gone. I opposed the war at its inception and hoped we could pull back before we became responsible for the wellbeing of the Iraqi people.

This being said one thing that really differentiated Iraq from Vietnam was that when backed into a corner, Bush had one of his few shining moments as President when he tied the troop surge to political reforms aimed at a more inclusive Iraqi government. One of the problems in Vietnam was that we were so used to propping up despots we were unwilling to confront Diem on issues of governance. At least Bush learned from that lesson albeit late and with his back to the wall (and I think further it is pretty damning that Bush's finest moment was one that merely managed to contain a mess he created).