Good scholarship, but I disagree with the conclusions. This collapse will be qualitatively different.

The typical Roman citizen lived rurally. Easily 90% of the food consumed was grown within a few kilometers of home. The slow decline and fall of the Empire over generations was not even noticeable to most.

Now over 80% of Americans, of people in developed countries in general, live in cities. The vast majority of them have no direct contact with food producers at all. And the combination of extremely long production chains, “just-in-time” inventorying, and a couple of generations of the government socializing losses for large companies have led to a brittle and fragile system where everything is interdependent — where even a few weeks of interruptions to the supply chain would leave tens of millions of people hungry.

And this system of industrial capitalism encompasses well over one hundred times as many people as the Roman Empire ever did (it peaked at about 60 million).

So unfortunately, the fall of industrial capitalism is going to be much faster faster, involve an order of magnitude more people and and thus be much harder than the fall of Roman Empire. (And let’s not forget the destruction of the biosphere and the climate emergency, which will continue to beat us over the head once we get out the other side.a)