Iraq is splitting into pieces militarily. Some of those political entities will never bother America so we should let them form their own government and work with them to protect our interests. The Kurds are the perfect example but other alliances may be possible in the future.
America needs to militarily stop the formation of a radical Islamic state in what’s left of Iraq. We don’t need a clear win but we can’t let future attacks from this area hit our homeland. It is better to make a deal with groups with a willingness to fight the radical Islamic forces now invading Iraq in exchange for future political power. The existing Iraq army doesn’t have a reason to shed its blood to protect a corrupt government that is destined to fail without American boots on the ground. An army that won’t fight is useless. Find an army that will fight and make a deal with it.