Why not just divide it now. Separate Iraq now. The Shi’a and Sunni’s don’t get along. The Kurds want their own country. SO stop the fighting. Each group gets their own country, the US signs an Oil pact to get their oil. And then the fighting should stop. Remove the reason to fight, or at least the “public” reason for the fighting and two things will happen. Either it will stop… or the real reason will be come apparent.
The outgoing British Ambassador to Iraq has noted that Iraq will likely go into civil war and then be divided.