I would say it is because of America's adversarial political relationship with opposing creeds: first atheist Communism and now Islam. The latter in particular, and the reaction to it (around the entire periphery), are the primary bulwarks of religious precept that endure. In those societies, religion still provides the necessary utilitarian function of harnessing collective action.
I doubt it. That is much too narrow a view. I don't think Islam has anything to do with it. Islam was not on the radar screen until 9-11, and the evil empire went out 10 years before. There was no sign of flagging religious faith in the 1990's. Religion is so much more personal, and micro, than some reaction to macro international events.