All religions have their radicals really. But generally war and poverty tend to worsen the problem. I'd say Western involvement is not absolved of all blame, nor is poverty (which is often a factor in any perversion of social interaction), but also that there is some inherent radicalism in the idea that we were all created by some Daddy in the sky that wants us to do his bidding or he will send us to a pit of fire to burn eternally.
Not opposed to spirituality or religion per se, but the idea that some deity cares enough to write out a little book of rules is the real problem here. Especially since said rules are vague enough that they can be interpreted however one sees fit based on the agenda they want to push.
So I'd say militant organized religion is the real issue here. Everything else, like foreign interventionism and poverty, add fuel to the already existing fire. The fire being an arbitrary book of rules, considered sacred and holy by a mass of people, that says whatever the churches and governmnts say it does.