It doesn't make sense. A total collapse of global civilization means that all major governments have been knocked off, which can only result from either a full-scale nuclear war, or an impact of an asteroid or something similar in scale. I don't really see that coming in the near future.
Of course one can always retreat to the woods or some remote places. There are people who do this and I enjoy watching their vlogs. But overall I don't consider it healthy to completely withdrawn from human civilization. After all even those vloggers use modern technology for transportation, vlogging and all other stuffs.
Depends on what is meant by 'global civilisation', but it has happened several times in many countries during the 20th century. The US has been immune to events like that throughout its short history, so there seems to be a very strong sense of "can't happen here", but it can. These things happen and people live through them. It's not a collapse you'd see in a Hollywood movie, in real life it is more mundane.
Just look at what happened with the collapse of the USSR, for example - that was just 30 years ago and affected a massive part of the world. Hyperinflation, many people had to resort to small-scale farming to feed themselves, specialists and academics with advanced degrees had to become taxi drivers and many older people had to resort to dumpster diving to survive. Crime of all sorts went way up. All sorts of factories/organisations/societies/buildings were near abandoned/were sold off for scrap and became derelict.
There was no collapse of global civilization or anything close to it in the 20th century. The collapse of USSR is indeed a tragedy event for their civilians but I'd not consider that a collapse of civilization. You still have a government. Yes there was an economic crisis but that's not a collapse of civilization.
I'd 100% agree if the wording is something like collapse of economy.
There was also a government during the collapse of the Roman Empire, which surely must qualify for any reasonable definition of a 'collapse of global civilization'.
The US going through something akin to what happened to the USSR would be a similar event for today's world, given the massive role that the US plays in the current world order.
You might want to re-read the wording in the post, which specifically said, "...political/economic/social complexity over a considerable area, for an extended time."
Depending on exactly how you interpret that phrase, there have been multiple country/regional collapses in recent history. As far as the USSR, it no longer exists. Sure, new countries replaced it, with some matching to countries that existed pre-USSR, but that country is gone. That seems like a collapse by any definition.
To add that I don't think a full scale nuclear war can wipe out all governments. I believe countries with vast areas such as US, Canada, Russia and China can still survive with a rather intact government.
Of course one can always retreat to the woods or some remote places. There are people who do this and I enjoy watching their vlogs. But overall I don't consider it healthy to completely withdrawn from human civilization. After all even those vloggers use modern technology for transportation, vlogging and all other stuffs.