Why won't America just get rid of "In God We Trust" and "one nation under god"?

Not everyone believes in god. America is not a religious based nation. Thomas Jefferson, one of the founding fathers, believed in the separation of the church and state. Yes, I know that phrase wasn't in the Constitution, but it would do great service to the Founding Fathers if we held this nation to most of their beliefs of this nation. Early Americans fled from English religious and belief persecution, and so that they may establish a nation that has no set guided beliefs but laws. Whoever says America is a Christian nation is an ******, because this nation is made up of very diverse peoples and ethnic, religious, belief backgrounds. Yes, I know Christianity is very popular, but that does not make this nation a nation under god. It is very sad to see people transform this country into something it was not intended to be.