Well, that is a given, but it is too broad. This disregards specifically Christian character of worship that marks America, the presence of the Frontier in our mental makeup and I would say the Nordic dominant ethnic character. Today, the "diverse peoples together" has become a liberal mantra and lost its attraction because of that.
The root of the West's decline goes all the way back to the beginning of Nominalism, with Ockham. Contrary to popular belief, I see the Scholastic period as the height of civilization. The intellectual seed of our decline was planted with Ockham. The first act in the decline of the West, and the slide toward radical individualism, was the Protestant Revolution. Since the Church was disestablished, we have steadily declined through Unitarianism, Rationalism, Atheism, Modernism, and now Post-Modernism.