Indeed, but for some countries there are too few players to really form a workable team, so exceptions are sometimes made to allow multiple countries to field a single squad. The most notable case is
BeNeLux, which is comprised of players from Belgium, Luxembourg (nominally at least, since there are no Luxembourgian players on the roster), and the Netherlands.
Benelux is a historical regional entity, so the SWC team based on it is at least somewhat justified. I imagine that a union of Norway and Sweden (and presumably Denmark, since Denmark too usually doesn't field a national team) would be permitted to join the league under the Scandinavian banner.