Fortunately for me, my son (and only child), Michael, lived for several years in Washington, DC, only two blocks from the Library of Congress, and my wife and I visited him frequently. When we did, I spent time at the L of C, much of it reading up on the treaty. I found some answers in the official Journal of the Senate. The President (by then John Adams) sent the treaty to the Senate in late May 1797. It was, according to the official record, read aloud (the whole treaty was only a page or two long), including the famous words, on the floor of the senate and copies were printed for every Senator. (It should be noted that the controversy about the Arabic version is irrelevant here: all official treaty collections from 1797 on contain the English version, and all include the famous words of Article XI.) A committee considered the treaty and recommended ratification. Twenty-three Senators voted to ratify: Bingham, Bloodworth, Blount, Bradford, Brown, Cocke, Foster, Goodhue, Hillhouse, Howard, Langdon, Latimer, Laurance, Livermore, Martin, Paine (no, not Thomas Paine), Read, Rutherfurd, Sedgwick, Stockton, Tattnall, Tichenor, and Tracy. We should ask ourselves whether we should not consider these 23 (and President Adams) great freethought heroes. In a very public way, they voted to say that "As the government of the United States of America is not, in any sense, founded on the Christian Religion, . . ." the Muslims of Tripoli therefore need not fear a religious war from the U.S. The vote was recorded only because at least a fifth of the Senators present voted to require a recorded vote. This was the 339th time (I went through the Journal for the first five Congressional sessions and counted them myself) that a recorded vote was required. It was only the third time that a vote was recorded when the vote was unanimous! (The next time was to honor George Washington.)There is no record of any debate or dissension on the treaty.
President Adams signed the treaty and proclaimed it to the nation on 10 June 1797. His statement on it was a bit unusual: "Now be it known, That I John Adams, President of the United States of America, having seen and considered the said Treaty do, by and with the advice and consent of the Senate, accept, ratify, and confirm the same, and every clause and article thereof. And to the End that the said Treaty may be observed and performed with good Faith on the part of the United States, I have ordered the premises to be made public; And I do hereby enjoin and require all persons bearing office civil or military within the United States, and all other citizens or inhabitants thereof, faithfully to observe and fulfill the said Treaty and every clause and article thereof."
What happened then? Did our heroes pay a heavy price? Skeptical that the public even knew about the treaty, I went to the periodicals reading room of the Library of Congress in, appropriately enough, the Madison Building. After some poking about I found out how to get access to newspapers of the 1790s, mostly on microfilm, but in a few cases I saw the actual papers of the day.
I found the treaty and Adams' statement reprinted in full in three newspapers, two in Philadelphia and one in New York City and, in one case, held the actual newspaper (the Philadelphia Gazette and Universal Daily Advertiser for Saturday, 17 June 1797) in my hands. There is no record of any public outcry or complaint in subsequent editions of the papers.
And what of our heroes? Well, none suffered any known negative consequences, and I've read biographies of each. One Senator, Theodore Sedgewick of Massachusetts, went on to become the Speaker of the House (imagine Newt Gingrich endorsing such a treaty! Henry Clay is the only other American in history to be first a Senator, then Speaker). Another, Isaac Tichenor, became Governor of Vermont, and then returned to the Senate for many years. Georgia's Senator, Josiah Tattnall (Georgia's other Senator was absent), did not return to the Senate, but he did serve thereafter as one of the youngest Governors in Georgia's history, and has a county in Georgia and a number of streets, squares, etc., named after him. (His father was a Tory; his son by the same name was a famous officer in the Confederate Navy.)
From our perspective these men may be heroes, but in truth the vote they cast was ordinary, routine, normal. It was, in other words, quite well accepted, only a few years after first the Constitution and then the First Amendment were ratified, that "the Government of the United States of America was not, in any sense, founded on the Christian religion." After a bloody and costly civil war and the passage of the Fourteenth Amendment determined that citizens of the United States cannot have their rights abridged by state or local governments either, religious liberty for all was established. Governmental neutrality in matters of religion remains the enduring basis for that liberty.