alt Hacker NewsCanada was my first guess, and I was able to get the rest of the Western hemisphere after that. I'm looking now for Portugal which i think should be pretty obvious, but I must be missing something.
Edit. Also, I was wondering why there was no French Guyana, but being part of France means it's not a separate country. However, in that case France should share a border with Brazil. I wonder what other such quirks are in this map.
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In addition to sharing a land border with Brazil and Suriname (via French Guiana), France also shares a land border with the Netherlands… on the island of St Martin/Sint Maarten.
Also, there's a new land border between Canada and Denmark, and not depicted on this map, since the border did not formally come into existence until 2022. https://en.wikipedia.org/wiki/Hans_Island#Resolution
I had a different strategy, starting with lots of connections, so I found Russia and China first. Albeit playing with a lot of mistakes.
I just did my first second-hand inference and it was satisfying. Turkey borders Bulgaria and Greece, don't know which is which, but those two both border North Macedonia, which was a correct guess.