In real life, there is one human universe with many countries, with different rules and stories in each country. You will notice that each of them has specific borders. Sure, you can interact with and travel to other countries, but once you cross their borders, you are subject to the rules and regulations of that country. There are no "universal rules" to Earth. Everyone is a part of their individual country, and each country has it's own thing going. Even in international waters, ships have to obey the rules of the country who's flag they're flying.

You could compare countries to types of RP as well. Except 'murica is the only Free one. The rest are Casuals. All the Advanced ones died off a long time ago.