Presumably the “You break it, you buy it” policy is operative.
I mean the USA “broke” Iraq and is responsible for the consequences. Obviously, the USA had no business breaking it in the first place. Nonetheless, a degree of responsibility ensues. How much responsibility now rests with Iraq is up for discussion. Staying out completely is probably not a reasonable option. Don’t think other parties won’t fill the breach (namely, Iran).
The sad fact of the matter is that it’s better to back an el-Sisi than a Morsi or al-Maliki. Talk of the return of Ahmed Chalabi is a joke. He is a proven liar, like his media flak Judith Miller.