I’m curious what depletion of resources they think caused the Roman Empire to collapse.
The RE collapsed mainly because of nearly constant civil wars, and those were caused by their never devising a legitimate principle for succession to power.
Any successful general could aspire to become Emperor, so Emperors were always (legitimately) of successful generals, and tended to execute them as a precaution. Which of course almost forced even successful general who might have preferred to remain loyal to revolt in self-defense.
It also meant, of course, that emperors tended to kill off their best generals, which left them more vulnerable to foreign enemies. With all its flaws, the later European principle of primogeniture at least meant general could concentrate on fighting the country’s enemies, and kings didn’t have to worry about them usurping the throne.
The Roman empire collapsed for demographic reasons. Too few Romans, especially those willing to defend the Empire. And, on the other side, too many barbarians who got ever more aggressive as Rome weakened. At first, Rome was able to co-opt the barbarian tribes. Starting with the Vandals, they eventually figured out that Rome was a paper tiger and started chipping away at the Empire. Rome was sacked a number of time, starting in the early 400s.
I see the same thing happening here. We’ve discarded the melting pot for multiculturalism. To our elites, Diversity = Strength, but in the end it will tear us apart.