Is God part of the American culture?

Yesterday I posted a question about the Founding Fathers being religious and the new Americans hating the whole idea of God. Most people answered that the state and the church are separated and that the Founding Fathers were not religious. However, Americans worship so much the idea of the "Pilgrims looking for religious freedom" in the sense of looking for a place where they could worship freely, and very often I hear presidents say "God bless America." So if this is what the American representatives and heroes show, why is it that there som many out there that deny his existence? Why are so Americans today against the idea of a God and some namy others claiming to belong to religion superfiacially?