Killed muslims in christian countries are more than killed christians in islam countries if we don't count war. If we count war, then comes a new question that "what they had there?"
Islam also has corrupted sects like Vahabi, Selefi. They don't accept others as real muslims and they are more near to terror and therefore easy to use them for imperial purposes. Christianity also has those kind sects like Evangelists, isn't it? They have an idea to help Jesus Arrival. When Jesus will come? When world falls in chaos and blood. So we need to put the world in war, chaos and blood for helping Jesus Arrival
Christians and muslims have one difference; Muslim terrorists are ignorant but mostly christians are wise.
Actually both of religion's members are used by materialist power. You may call them Illuminati, You may call them Global financial monsters.... Whatever if you call them they are managing everything on world. They aren't atheists but worse of being atheist. They are satanist
I think if the reason behind killing is religion then there is something really faulty. That goes for all religions, suicide sects and other things like that.
I know christians were quite murderous in the religious wars in the middle age, muslim countries were developed farther then christian ones. Now we have some kind of opposite direction.
I don't think that the US fights as christians. George Bush only used this "God told me to attack the iraq" as a stupid reason, maybe he could draw in some radical christions.
And yes, there are powers, mostly out for money and power, that try to use local groups and such to reach their targets.
I doubt though that ISIS is somehow guided by another power. I think they are independent.