The Constitution does not require a separation of church and state, notwithstanding what Thomas Jefferson wrote about it.  Jefferson had no part in writing the Constitution; he was in France even when the Constitutional Convention was held.

Nowhere does it say that the government or its members must be secular.  

The Bill of Rights is a restriction on Federal government power over the People.  The First Amendment prohibits the government from imposing a government religion on the People, from making laws about the practice of religion, and from restricting people on practicing their religion.  

The Federal Government through its officials can espouse, e.g., a belief in God, a belief in transubstantiation, a belief that Jesus is the savior, and that Joseph Smith was a heretic.  As long as it does not mandate those beliefs on the People, it is Constitutional to do that.