That's the thing: We did exactly that in Afghanistan. After attempting, and grievously failing, to set things right there, we pulled all our troops out, and it just became a breeding ground for terrorists who hated the U.S. because we did what amounted to a hit-and-run there. That's a good part of the reason why 9/11 happened, and I can guarantee you we'd be complete idiots if we made that mistake again (although, seeing as we've made so many other mistakes again lately, it wouldn't exactly be an unprecedented event). Pulling out of Iraq completely is the worst thing we could possibly do for ourselves right now.