One of the things that most interests me about America is that whilst it has more active christians then pretty much any other western country, and easily the most in the anglosphere, it is the only anglosphere country (and probably only country full stop) in which people say "Happy Holiday!" Instead of "Merry Christmas" 
People still say "Merry Christmas." but the problem is that you don't know if someone is perhaps, say, Jewish. So unless you know the religion of the person it is better to simply say "Happy Holidays."
