They added "In God we Trust" on the bills in 1955 and "One Nation Under God" was added in 1954. Both were answers to the cold war and the communist scare. To say in one line that you "completely believe in separation of church and state" then basically say its ok they use religion as a reasoning to write policy is an oxymoron. Religion is a tool used by the ultra wealthy and those in power to stay in power.
Heck, the church was pro abortion until Reagan and Jerry Falwell teamed up and made it their number one issue during the 80s. Reagan wanted the christian vote and Falwell wanted a spot on his cabinet.
We aren't a "christian nation". The entire reason why we even exist as a country was because a group of people didn't want to be forced to join the Catholic church. We, as a nation, are supposed to be a melting pot of ethnicities. A diverse group of people and religions. THAT is what our forefathers envisioned for us. There's a group of people who seem to forget this.