For Those individuals who still believe the United States of America was, in some way, built upon a Christian doctrine:

Art. 11. As the Government of the United States of America is not, in any sense, founded on the Christian religion; as it has in itself no character of enmity against the laws, religion, or tranquillity, of Mussulmen; and, as the said States never entered into any war, or act of hostility against any Mahometan nation, it is declared by the parties, that no pretext arising from religious opinions, shall ever produce an interruption of the harmony existing between the two countries.

From: The Treaty of Peace and Friendship between the United States and the Bey and Subjects of Tripoli of Barbary, Article 11. This treaty, authored by American diplomat Joel Barlow in 1796, was sent to the floor of the Senate, June 7, 1797, where it was read aloud in its entirety and unanimously approved. John Adams, having seen the treaty, signed it and proudly proclaimed it to the Nation.