Seriously, I don't think there are any good options, including disengaging. The Kurds have always seemed to be the group most open to us since we protected them with a no fly zone, but aligning with them always causes major problems with our Turkish allies.
No, there are no good options. Had we been more careful in the battles we have already fought, perhaps we could actually do something drastic in this case. I believe in the military, but I don't think we have the political or societal nerve to go down that road again any time soon.
And regarding any such invasion with ground troops, it would take a brutal all-out political incorrect effort. None of this business of fighting with one hand tied behind our backs for political correctness that I feel we did in Iraq and Afghanistan. I believe our military kicked a lot of butt in those two conflicts yet were still hamstrung by stupid regulations. Again, JMO.
As for any business about fulfilling their apocalyptic prophecy by putting boots on the ground over there, I could not give 2 rips. I guess as atheists are to all religions, I am to theirs in particular.
In the end, I could not say what would be best for us to do but I know that somehow the world is going to have to rise up and stop these psychotic savages.