at this point it would be like closing the barn door after the horse has left.
short of us completely walking away from everything we're involved in in the middle east, something that seems impossible to do, ISIS has too much skin in the game to just say "that's it, we're no longer going after the great satan. come on, boys, let's go home." the fact that they've got (presumably) sleeper cells all over europe and the US says they're not going to give up any time soon.