One thing I would like to add about the topic in general. In my political science class in college, the professor acknowledged that everyone knew that God on the money and other tradition religious entanglements should be struck down by the Supreme Court, but no wants to for the simple reason that if anyone pushed it far enough for the Court to actually take action, the backlash would probably be bad enough to force through an Amendment specifically allowing it, and perhaps a lot more.
If put to a popular vote right now, we would probably be declared a Christian nation.
Jonathan