From the point of single node it would only mean that you lost some connections but you are able to quickly find replacements. At the end now, when you have your node and you are connected to 10 other nodes, you do not know if you are connected to Asia and Australia or to your neighbors on the next street
Each country have different IP address allocation, so you could make educated guess based on other node IP.
ip to location may be helpful indeed, for not-tor connections. It would be interesting to have something like a quota for different continents/countries.
there is no criteria for nodes selection, is there?
It depends on which full node implementation you use. IIRC Bitcoin Core avoid make connection to multiple nodes with same IP block.
Interesting, I did not know that. There may be speed test, but it would favor close nodes, so it is not the best solution.
So, as I understand if let's say one country with power big enough to mine blocks is disconnected, they build their own chain, but their work will be lost after reconnection.