Actually, although I strongly favor separation of church & state, unconstitutional is hard to discern here. How long has 'in God we Trust' appeared on our money? Is THAT unconstitutional too?
What if we said 'atheism shall be the official religion of the US; any official mention in text or symbol of a deity is prohibited' -- would that be unconstitutional? It's a question I think needs to be asked because that's where we're headed.