the discussion has / is very detailed here. i am just a bit intimidated to join in but will give it a shot.

Yes the insurgents, in my estimation, are very afraid of the Shia and Kurd militas going after them. The gloves will come off and the insurgents along with many other sunnis will pay the price. The problem comes when the sunni minority sees that they are being brutalized and decides they must fight back.

Our worst case scenario is a failed state with an enduring civil war. See Lebanon times 20. Continued training, mostly in restraint and rule of law, to develop a professional military instead of armed gangs and assination squads is the only way out that is favorable to the US. El Salvador is an example of what can go wrong when militias are unleashed. I think the availability of weaponry and large condensed population centers would make it much worse than anywhere in central America.