It strikes me that America is not so exceptional at all.
Its just a case of a more efficient technology wiping out a less efficient technology. Yes I am speaking of the genocide of the Native Americans. This is an ancient theme in our species.
The reason the European culture was more efficient (note I do not say better or superior) was that it was highly centralized power dependent upon easily accessible raw materials that can be exploited by such centralized power.
Problem. Once those easily accessible resources are exhausted, then the centralized culture dependent upon huge scale technology for its power can no longer function. It literally starves to death. At that point cultures reliant on smaller scale technologies that can be supported on a thinner resource base become the fittest to survive.
This is also an old theme. Power accumulates in the center and persists for a while and then collapses.