Christians believe that their citizenship is in Heaven, and while it is true that this place will be the ultimate destination of our citizenship, Christians also have citizenships in their towns, states, and countries. Paul himself envoked his citizenship status as a Roman in the book of Acts. As for the question of seperation of church and state, purpose of the Amendment by the Founding Fathers was not to keep religion out of the government, but to keep govenment out of religion.