But only true in part. You are not disallowed from practicing any religion as long as it doesn't violate US laws or others' civil liberties. It is not legal to "practice" one's faith in a courtroom- or any federal or state building. Of course, there are always exceptions, such as allowing Muslims the ability to pray throughout their day. I'm sure you all see the ongoing debate in the US concerning the Ten Commandments and displays of Christmas... And of course, we still swear on Bibles when sworn into public office or in courtrooms.