One thing our continued presence in Iraq does, of course, is dissuade other regional actors from direct military intervention in Iraq. Except, of course, on days when (as Eric Martin points out), the Iraqi government says "Turkish artillery and warplanes bombarded areas of northern Iraq on Wednesday."
There are at least two shoes that haven't quite dropped yet in Iraq. One is the Kurd-Turk situation, involving both Turkish military action in northern Iraq, and Kurdish guerillas moving back-and-forth across the Turkey-Iraq border. The other is that Iraq's constitution schedules a plebiscite to determine the status of the Kirkuk region (i.e., in Kurdistan or out) and there's little reason to think the losing side will accept the outcome of the vote peacefully.
Photo courtesy of Kurdistan4All.