...between Vietnam and the current situation is that there is not another superpower in the background supporting the opposition. Just as we reciprocated in Afghanistan, the Soviets more than willing to engage us vicariously.
From the standpoint of Iraq, it's unlikely that anyone's going to come to Saddam's aide. But once you get rid of Saddam, there's a vacuum. The Baathist aren't going away - Syria will see to that. The Kurds and Shias will have their axe to grind. The Iranians are going to see one impediment to Persian expansion replaced by another. The Turks used to own this stuff as an empire. The Soviets and French want their business interests restored. The Saudi's aren't going to like have their monarchy undergo scrutiny.....