Even though there was a United Earth, each region still retained its independent identity. Much as how Wales, Scotland, and England still have their identities and how each of the 50 United States have their own identities.
Maybe the European Union would be a better analog, as we don't know the provincial government structure of the United Earth government. Would the United States still have a President, Congress, and Supreme Court? Would each of the states still have Governors and and State Legislatures? Would there still be county officials and city majors? I would assume yes.