"congress shall make no law respecting an establishment of religion" means the U.S has no officially sanctioned religion. As the word was originally used, "religion" does not apply to atheism. It is not an organized religion and has no doctrines. Lacking belief in a claim it is the automatic starting point until it has been proven sufficiently, reliably, and repeatably to in fact be the case. ...just like our court system, I might add. God is accused of existing, and there ins insufficient evidence to demonstrate it, so he is "not guilty", which we all know is not the same as innocent. God MIGHT exist, but nothing points to that. Doesn t matter if it s pixies, unicorns, bigfoot, aliens, or god himself; they re all beyond what we can see or detect in any way, and therefore they re beyond what we can even prove is a real possibility.