I don’t think there has ever been a setting for choosing country. The country it consider it’s home country and most of the animals in the animal dealer will come from and probably animals born is defined for some maps in the code. So it is only a small list of maps that have country defined there. If a map is not defined there it defaults to UK.
I have an issue registered to add a savegame setting though, but have no idea of when I’ll get to it. https://github.com/rittermod/FS25_RealisticLivestockRM/issues/35