As Adam Schiff of Law and Order would say Make the Deal.
Cut deals with these various groups, use their help to kill those who still want to fight, set up some stronger regionalism so that Kurds, Sunni and Shias can stay out of each others way.
Transition so that things calm down enough so that the US can buy off the UN to put in peacekeepers. I figure $20-40b per year should do it for 20,000 blue helmets.
btw: My political view is one of pragmatism and real politics. Look at the actual balance of power in a situation and the goals that you want. Achieve your short and long term goals at the lowest cost.