Yes, one nation under God!
No, 1st Amendment!
It should be because when the pilgrims came they trusted in God trusting God makes a better and stronger nation.
The US was founded on secular principles and it would make no sense to make an official religion now.
I'm a Christian and I would be happy if this were so, but eh it's a little too late for that lol.
No, it was founded on Christian principles, but it shouldn't be the official religion, or it could start persecuting people for not conforming to the official religion.