No I anticipate that it could take days or weeks for a given message to hitch a ride all the way around the world. It would have to be rather important for so many people to decide to allocate space on their devices for it. (Whether that's automated or involves a human in the loop would be an app-specific detail).

Of course you could sort of fake locality by piping it through the traditional internet, but the point is to design something (an alternative to IP) that would be resilient even when the traditional internet has failed so using the traditional internet is sort of cheating.

As far as access... I'm not really sure what that means if we're addressing content and not devices. A node isn't going to pick up some data unless it finds that data to be interesting for some reason--likely because it bears a signature from a trusted individual and the cryptography checks out re: its not having been tampered with. If you're assessing trustworthiness based on content there's no need to scrutinize the device you got it from.

Also I apologize I haven't been making a tremendous amount of sense. I think I've maybe had COVID brain for a few days and only just now have I become fully aware of how impaired I am.

Why would anyone adopt this system, even as a backup, when the postal system already serves as a backup communications network? And has already proven its performance?

And in such an extreme scenario I imagine roughly no adults will care about any ‘content’ at all, food, water, and shelter would overwhelm all other nice to haves.