Eric Alterman repeats the mantra - and gives us a host of reasons to really believe it:

Unlike Vietnam, our allies are treating the local populace well and are fighting effectively.

Unlike Vietnam, our troops are not torturing anyone or committing any atrocities anywhere.

Unlike Vietnam, our allies are committed to democracy, and are capable and experienced in carrying it out.

Unlike Vietnam, we are backing strong, independent leaders, rather than quislings and puppets whose power base rests with our military forces and economic support.

Unlike Vietnam, we are beloved by the people we are saving.

Unlike Vietnam, our president and his cabinet officers are leveling with the nation about the costs of victory and likelihood of defeat.

Unlike Vietnam, we have the support of the international community.

Unlike Vietnam, we have the whole thing well-planned out.

There are surely more. Build your own! Fun for the whole family! Here, for example, is a real reason why Iraq is not Vietnam:

Iraq's urban guerilla warfare doesn't really offer defoliation as a strategy. You can't drop Agent Orange on a city. Well, I guess you can, but that's more of a long term strategy . . . or maybe not.