There are nearly one million Google entries
for the precise words 'decline and fall.' The three most famous books
on the subject of civilizational decline and fall are by Edward Gibbon, Arnold Toynbee and Oswald Spengler. There are many books using this concept and applying it to the U.S.
I'll state the facts bluntly. The notion of historic 'decline and fall' is misleading, irrelevant and virtual nonsense. It is a concept advanced by people who have a Euro-centric world view that is at its core eschatological. If one looks at the Roman Empire, Greece, Egypt, the early America's there are many examples of civilizations that rose and fell.
On
the other hand China, Japan, India, Persia and a number of other
civilizations are still with us after thousands of years, not to
mention the one that disturbed Toynbee the most: Israel. These
civilizations have had many ups and downs but they are still with us. They all made it into the industrial commercial world and are adapting.
The notion of a civilizational rise, decline and fall is, as I said, misleading, irrelevant and virtual nonsense. None of the historic examples I just cited can be used as evidence of decline and fall. There is no reason to believe such a concept applies to the U.S. unless it is wishful thinking on the part of people who wish us ill.