"By the authority vested in me by the state of ____, I now pronounce you husband and wife." Here, the minister acts as an agent of state not as an agent of God. The state recognizes the Christian wedding rite as consumating a civil contract. I wonder why the ACLU hasn't objected to this?

Assuming the minister properly verified the consent of parents and the posting of the bans, he should know that the Christian couple was pronounced husband and wife by God prior to the wedding rite. As the agent of God, he should merely publicly announce that the couple are husband and wife.