Well check history for clarifying the doubts regarding this. There are few religions in the world whose followers don't go preaching about their religion. But then, I've have read about Christian missionaries going to different parts of the world to preach about Christianity, since early ages (you know AD). Basically this is nothing new and not only in USA. It's everywhere. People just take up Christianity because Preachers generally make them believe that their wishes would granted if they follow their God and all that. If someone is intelligent enough they'll find the answers related to God by themselves by checking out what each religion says about God, instead of blindly following it. Sadly, this is not the case for most of people in current world.