As a counterpoint i think people are too sanguine about writing off the destruction and dislocation of a once stable society, often because it was hard for contemporaries, and hard for our imaginations, to grasp the full magnitude of disasters inflicted, because the litany of disasters, sacks and conquests all runs together on the page, and recent scholarship bringing “light” to the Dark Ages sometimes makes it hard to weigh exactly how terrible a disaster was on local scales compared to the steady march of continental developments.
Imagine the short fictional account of future history;
“During the Sino-American war several cities on the West Coast were sacked. In 2117 the Chinese leader, Xiang Shu, was ambushed during his withdrawal into the Sacramento Valley by Californian partisans. In retaliation, he sacked San Fransisco. Its main buildings were destroyed, all its bridges cut, its male population killed and the women and children sold into slavery.”
Can you imagine a whole American city wiped out in that way, especially one that was the center of culture and trade? Imagine this happen to almost every American city over a 200 year period. Would that be called a smooth transition to the post American age? What would it be like to live in such a time? What if half the population of the US were rural 200 years from today, and the largest city has 2 million instead of 20 million?