In Robert J. Meyers' letter, he described the results of his research into the 1797 Treaty of Tripoli, of which Article XI is often cited as stating that "the government of the United States is not, in any sense, founded on the Christian religion." While Meyers correctly notes that the Arabic version of the treaty contains no Article XI, he is mistaken when he states that "the approved treaty does not contain any language to the effect that America is not a Christian nation."
In fact, all English language versions of this treaty contain Article XI with the above language. This language was present in the treaty as approved by the Senate on June 7, 1797 and ratified by President John Adams on June 10, 1797 as may be verified by examining the Congressional Record or any treaty collection (the treaty is 8 Stat 154, Treaty Series 358). It was the English version of the treaty approved by the U.S. government, not the Arabic version.
Perhaps Meyers is confusing the 1797 Treaty of Tripoli with the treaty of 1806, which, among other changes, eliminated this language. I am uncertain as to how he came to his interpretation of the facts, as it bears little resemblance to that presented in pp. 1070-1078 of Bevans' "Treaties and Other International Agreements of the United States of America, 1776-1949, vol. 11," the very source he cites.
[Note that the 1805 (not 1806) treaty contains similar language, minus the "not, in any sense, founded on the Christian religion" phrase: http://www.yale.edu/lawweb/avalon/diplomacy/barbary/bar1805t.htm#art14. -JJL, 4 October 2007]