They avoid the chaos of a collapsing civilization by keeping a low profile. Most of my own ancestors were in the U.S.A. at the time of the Civil War but there are no family Civil War stories. Likewise the "Dark Ages" of Europe probably were not so dark for people who escaped the notice of historical empires. My ancestors likely didn't miss the Roman Empire at all. Good riddance to them and their roads and their aqueducts and armies. Much the same as the Inuit probably didn't miss the Scandinavians in Greenland.
Cultural regions that reject birth control and have little tolerance for non-violent anarchy are in for some tough times. It's the fundamentalists, racists, nationalists, and sociopaths of all stripes who will actively kill people or callously allow them to die.
Cultures that cannot adapt to new environmental conditions will die but not necessarily the people of those cultures.
I don't think "Democratic" and "Authoritarian" labels are useful here. From the perspective of a dissident, both sorts of society impose upon me in unwelcome ways. For example, I find the automobile culture loathsome. Automobiles kill and maim people, they isolate people, they cause severe damage to the environment, and generally they stink. Even though my wife and I abandoned the automobile commuter lifestyle many years ago, automobiles are a cultural necessity in our community. Fully functional adults are expected to have cars. Children, people who have had their licenses revoked for drunk driving and other offenses, blind or otherwise disabled people, and recent immigrants (mostly undocumented farmworkers) are the only people who don't have automobiles.
There are ways of transforming an automobile based community into a walking, bicycling, and public transportation community, but that's probably not going to happen until economic "degrowth" makes owning and operating an automobile too expensive for the majority. Recent farmworker immigrants here live in dense communities, very roughly converted 'fifties era suburbs, and connect with the labor buses in the supermarket parking lots.
If the U.S.A. is unable to correct the growing disparity of wealth, and we are unable to significantly reduce our environmental footprint, our "middle class" is going to be living in conditions very similar to those of the recent immigrant farmworkers in our community.
= new reply since forum marked as read