That's not his idea, but more of an inevitable result that he predicts. The main indication of that currently is collapse of bipartisan system that can be observed at the moment. Long story short, U.S. is at the verge of collapse of its political system that is like 200 years old. And as a bonus he indicates a cultural vacuum with decrease of WASP in population, resulting in U.S. turning into latino-american type of country.
I don't say I buy this article in its entirety as well (the author is widely controversial and a number of his points are rickety at best), but the look at current situation from civilzational point of view is nevertheless interesting.
P.S. I do, however, stand on position that U.S. is on the verge of major economical and political turmoil that can be compared with Russia in 1910s or 1990s. And that means huge with millions of demographic losses. I do also think that this is kinda inevitable, and what you have control over is size of losses.
Edit: As for the gradual decrease, I'm not sure there are any examples of such in the history of humanity. Every single major geopolitical power declined slowly at first, but then went down with a big bang. Rome, Spain, Holy Roman Empire of German Nation, France, Great Britain, Russian Empire, Austr-Hungarian Empire, Soviet Union. Perhaps Great Britain may be called an exception, but then again, if you're up to calling World War II something insignificant :)
Edited 4 time(s). Last edit at 05/23/2017 02:22PM by Kstatida.