If Lemmy and other fediverse discussion areas had developed slower and more naturally there might have been more of a country/instance symmetry, but anyone who was around when the Reddit implosion and migration happened knows that it was total chaos and a grab bag of where a new user should sign up. Lemmy and the rest were not ready for such a shift, and now that everyone’s been in a place or two for a while, short of a closure or blocking or whatever there’s no reason to move around to a matching country and instance, if there even is one. People mainly look for popularity, activity, themes, and engagement, and if that’s found on the other side of the globe it works.
Probably trying to mirror Reddit, which had /r/politics for US, and /r/worldnews for everything else. There was a lot of effort (probably wrongly) to try and copy Reddit over instead of finding new ways to do things. /r/worldpolitics was the original sub, but there’s an interesting drama story there.