In Vietnam, the North Vietnamese were supported by the Soviets and (to a lesser extent) by the Chinese. The Soviets poured in tens of millions of dollars worth of material, provided extensive training via "advisors" and even flew some of the MIG aircraft against our guys over North Vietnam.
In Iraq, there will be covert support from Syria and Iran - and that's it (other than hundreds of Al Queda wannabes, which is great, since they will all flock to where our guys can kill them).
In Vietnam, there were jungles to hide in, our technology was far more primative, and the people were predominantly a single ethnic group. Religion was not a dividing factor.
In Iraq, there are Shiites, Sunnis, Kurds, and a sprinkling of other folks like Turkmen. They don't get along with one another. The Sunnis and Shiites have been killing each other at least as long as they have been jihading against the "Crusaders" and "Jews".
So -- no matter how the DemonRats try to frame it -- Vietnam it ain't.