This was ratified by the US Senate....when many if not most of the Senators were also the "Founding Fathers". Certainly most of the "founders" were still alive.Treaty of peace and Friendship between the United States and the Bey and Subjects of Tripoli of Barbary.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.
The United States is not a "christian nation".