ISO 3166-1 would provide a superset of the proposed list (249 countries vs. 195): it includes member states, members of UN agencies, and country and region codes defined by the UN statistics division. It therefore includes not only member and observer states, but also countries like Taiwan. And there is a mechanism for user-assigned codes which could be used for places like Scotland or Catalonia, where some users may identify with a nationality that isn't officially involved in international politics.