Not disagreeing with you over all, but the pull out of troops from Iraq was exactly on the schedule set by the Bush administration (http://en.wikipedia.org/wiki/Withdrawal_of_U.S._troops_from_Iraq)
Obama was pretty much locked in to keeping the troops there that long by the departing Bush admin. Obama would have had to re-negotiate the agreement with all the partners to keep the troops longer or to remove them prematurely. And negotiating things is like hard and stuff so you know the Dems weren't going to go there.
Both administrations have pretty much proven that we should have never set foot in Iraq after 9/11. Because we did, we will have to deal with the mess we created (and its consequences) for the next few decades.