Terra

The homeworld of humanity, Terra is the shining blue and green planet with the highest concentration of livable resources known in the solar system. It is also the only planet with a self-sustaining biosphere. Nearly 3/4th of all humanity still reside on Terra and it is a central hub of politics and organic resources. Though Terra still has many nations, it is overseen by a global government called the United Nations of Terra (UNT) which seeks to protect Terra's interests and ensure the security of their world from outside threats be they political or astronomical.

For locations, you can use real-world nations. Borders and titles and relationships have changed since modern day, but not by much.