Perhaps President Bush would be one of the greatest American Presidents ever, even better than Ronald Reagan. I just think that may happen.
If I could go back in time, I'd tell GWB several things he must do:
No troops on the ground, aside from Special Forces hunter-killer teams. No nation-building: Afghanistan will have to stop fighting among themselves and build their own nation, when they are ready.
Finally, leave with a warning: if you don't mind your own business and we have to come back again, we won't leave ANYTHING standing. And, if we see you build anything bigger than an outhouse, we'll drop a bomb on it.
This isn't hindsight. In the run-up to the second war in Iraq, I posted something to the effect of what Biden actually proposed later (and one of the few times I agreed with him): Iraq will just degenerate into factions fighting each other, and we don't have the political will to stay the course. The only way to a lasting peace is to separate them.
If the US did ANYTHING in Iraq, we should have said: We recognize the Kurds as a separate nation. If the other two factions try to attack them in any way, we'll bomb you back into the Stone Age. Let the Sunni's and Shiite's work out their differences, or keep fighting -- it's their choice, but we stay out of it.
Yes, I'm sure I'll get flamed for this, so I'll put my Nomex suit on.
But, I'll reiterate: I don't think Bush is a bad guy. I don't think he did anything intentionally to screw up the US, unlike his successor. But, he made mistakes, and they were colossal ones that he should have known to avoid.