Regardless of whether you feel that Iraq was a mistake, shouldn't the question now be: "how do we move forward?". Anyone with a reasonable measure of common sense, intelligence, and reading ability can see that Iraq should never have happened, but it has.
I'm in Australia, and many (the majority, but not me), supported Australia's involvement in the campaign (yes, most Americans do not realise this, but Aussie troops, jets, and ships fought alongside the US and British forces).
Now the majority here believe that it was a mistake to invade, but we stand by our government's commitment, and I doubt that more than a small percentage would support withdrawing our troops before the "mission" has been completed.
If the US backs off now there will be no stopping the terrorists. The situation is definitely a mess, but I can't see any way out, other than progressing forward, now. Bush has to finish what he started. Hopefully he will take a little more care with his next project.