The mystery is why anyone would take this nonsense seriously. The answer, I believe, is The Book of Mormon's assertion that Jesus Christ walked on American soil and that native American were one of the 10 lost tribes of Israel. The latter association has been conclusively refuted by DNA evidence, which shows no genetic link whatever between native Americans and Jews, but no matter. The attraction of this silly doctrine is that Americans might have their own American revelation, with American references and an American history. In other words, it is driven by resentment against the unpleasant fact that Americans remain beholden to the history of the Old World.
Spengler, as usual, practices a questionable psychoanalysis from a distance, but even so he's a good read.