Well, you can keep saying that the coalition should hold out in perpetuity, the situation really does not look like it's going to stabilise and the coalition does not posess any measures to make it happen, all it can do is force a local temporary lul in the wake of a major offensive/crackdown.
All the coalition is doing is making sure the government is not overthrown, and with presidential elections looming in the US, that guarantee can't even be confidently made.
As for the bigger picture, the indication that you are somehow limiting terrorism, and 'fighting them in Iraq rather than in the US' seems like a leap of logic to me.
The mere presence of American troops in the middle east is, it would seem to me, an enormous boon to the international islamist extremists.