One can point to several factors, but here's what can't be denied:
-a certain Iraqi dictator kept these wackjobs in check
-we deposed said dictator for "iffy" reasons
-no dictator = power vacuum
-a weak govt is installed
-weak govt invites turmoil led by former soldiers of dictator
-chaos ensues
What happened in Syria?? If IS is Americas fault then we must have caused it there too right?