I hate it when people compare Vietnam and Iraq. They're just not the same.
For one thing, In 'Nam, the enemy was a more unified and better organised insurgency. In Iraq it's several groups fighting each other and the coalition.
In 'Nam, the objective was to contain communism. In Iraq there isn't really one, it's the more the result of an intelligence ****-up.
In 'Nam, the terrain was also radically different. 'So what?' you might ask. Well, when you're dealing with an insurgency, the terrain dictates quite a lot of how you do it and what goes on on the ground.
'Nam was also on a much larger scale, I believe. I don't have troop figures to hand but I'll look this up. I could be wrong on this one.
Political backdrop of 'Nam was also extremely different. It inspired real rage in people whereas Iraq has done to a lesser extent but for the most part has just inspired strong disagreement. I'm not sure why but I'm guessing it's related to the reasons above.
In 'Nam, the insurgency was actually effectively beaten on the ground after the Tet offensive. And the violence in Iraq has notably decreased after the 'surge'. As have US casualties. That's a point of comparison I guess. But it's still tenuous.