I think the route cause of all the terrorist activities lies with muslims all over the world. It is very clear that where ever terrorism is prevailing, it is due to the muslim fundamentalists whether they are in America, Europe, Middle East, India, Afganistan etc. These muslims don't work for world peace, rather they spread hatred all over the world against all other religions.
it is better that all the citizens of the world should get united against these muslims and try to eliminate these fundamentalist in a way they better understand i.e. war against them and the action should be very strict one.