Earth

Earth is the 3rd planet from the sun in the solar system. It is the only planet to support life in the solar system, and is colonized mainly by humans. Originally thought by many of it's inhabitants to be the only planet to support life, after hundreds of years, other earth-like worlds have been discovered and colonized. As such, Earth is now the center of a large network of human civilization across the galaxy.

Nations
Many countries that existed in the 21st century still exist, including the U.S.A. and as such, war is still found on Earth. Each nation have been populizing planets to increase their dominance throughout the galaxy. As Earth is a center point for this vast network, whoever controls Earth, controls all other planets colonized so far.

The Moon
The moon, though barren, has a U.S. military base and factories for production, and has been partially colonized by humans.