Hi

Surely this is not a new question, but I did not know what to search, so I apologize if this is a repeat. That said, I am hoping someone can shed some light on how bitcoin would behave in a hypothetical future scenario:

1. Consider a scenario in which the internet no longer exists, in that it has been broken up due to some sort of strife causing the internet backbone and ISPs to no longer work. Probably we won't have electrical grid either, but many crypto-minded people I know are prepared for this.
2. Say these people, members of their respective communities, create their own networks, effectively creating an internet (or intranet) for their own communities. From here they can serve their community many services. i.e. backups of wikipedia, provide various services, entertainment, cell service via open source solutions, etc.
3. One of the many services these communities can and will probably implement, is bitcoin, and they continue to mine blocks.
4. Many of these communities exist, and thus, many independent bitcoin chains (forks I guess?) with different histories.
5. Some years later, the internet backbone is re-enabled, and these bitcoin nodes across all these disparate communities now can reach each other.

What happens? Does the "longest chain win" and thus all communities, except that which had the longest chain somehow, are now considered untrue -- effectively reversing the transactions of all communities that reunify except the one that happened to have the longest chain?

Is there a cryptocurrency that is better suited to this type of fragmentation->reunification series of events, or does bitcoin handle this?

Another way to put it is how would these disparate bitcoin merge multiple histories and provide a managed way to deal with those "merge conflicts" ?

It seems to me that once fragmented, nodes should never re-unify, and should instead trade against each other on some market. i.e. BTC-CommunityX and BTC-CommunityY would have to both exist independently... but what if you're not an expert at blockchain and you're just the community member standing up all these services and bitcoin just happens to be the solution you went for, and suddenly the network reunifies, all your history is suddenly lost?

Thank you.

edit: fixed a run on sentence