There is no complete separation of church and state in the United States. There is no government document which directly states verbatim that they must be separate. There are some separations, such as article 6 of the constitution and the first amendment, but there is no all-encompassing separation, nor is there anything that says the state must be secular. Just non-denominational.
You really believe in a man who has helped to save the world twice, with the power to change his physical appearance? An alien who travels though time and space--in a police box?!?