Don't see why it should have been .... it's been sitting right there on the bookshelf for over 97 years, ever since Oswald Spengler wrote Decline of the West. Nobody's ever falsified Spengler's thesis, and America is part of the West.
(Some people associate Spengler with Nazism, but he broke with them in 1933 over his pessimism about the future of the West and his refusal to endorse Nazi racial theories. He died between the wars, having predicted the demise of the Reich.)
Interesting. Thanks.