If Rome Collapse - then it didn't occur to the people who lived through it ~ historians regard the 'collapse' of Rome as having lasted 300+ years at a time when the life expectancy was in the 30s to 40s and after the collapse did occur general nutrition and living standards actually improved.

Rome itself didn't disappear - people continued to live within Rome itself and the 'Roman Empire' technically got bigger, if we regard the Roman Catholic Church as being the proper continuation of the Empire.

True collapses rarely occur in history - they're more like fades into obscurity and often whimpers at that.

Maybe the one exception was the Soviet Union where the collapse was almost instantaneous to the American perspective, although the Soviet people themselves were well evident it was a dying institution at best.