Except Christians have moved on, it's not that long ago they went to the middle east to butcher the unbelievers in this holy crusade. The Islam is representing the dark ages, the key issue is globalisation. It's not just a problem in some location in the world, it's a problem that is everywhere.
Taking over any western country is not going to happen, not anytime soon atleast, the western world would come down brutally if that would be the case, probably escalating the conflict even more. The sole reason why ISIS is having a foothold is because of the fragile situation in Syria and Iraq (and Libia), same with Boko Haram in Nigeria. And the reason why people in those countries either flee, accept or join them is because they are afraid, afraid of being murdered for not having the same believes, but also afraid of the alternative. Alot of them simply pick the side that gives them the most stable normal life.