Why does the US allow these pagan religions, when those gods don't even exist?

Well if the framers of the constitution went that route, then there would be no Muslims in the US, probably no Jews, And only a handful of different Protestant denominations. But since many of the colonists came to the colonies to practice the religion of their choice, and because declaring a national religion would divide, rather than unite the colonies as a new nation, the frMers wisely chose to create a secular state and by law, separate it from ANY religion. That is why there is no national religion. People here are free to believe, or dis-believe, whatever they like so long as they don't break laws ( like human sacrifice is not allowed). It is one of the reasons, in my opinion, that my country has come so far so quickly. Imagine from going from a set of backwater colonies and a penal colony (yes Georgia and Austrailia have that in common) to a world superpower in less than 200 years.