God Bless America started to become an almost ritualistic incantation at the end of political speeches really with Ronald Reagan. It appears occasionally before, but it was not that common. And of course since it was a song that wasn't written by Irving Berlin until the 20th century (laughter), none of the 19th century presidents said God Bless America at the end of speeches, either. I think that the symbolism which suggests that everybody is religious and that even presidents who believe in church and state feel obliged to do this.