The Colonial Alliance of Earth (CAE) most commonly referred to as the Colonial Alliance or sometimes simply The Alliance is a republic responsible for the governance and defense of a large federation of extra-solar colonies and it is the representative nation of Earth. While colonies fall directly under Alliance control the nations of Earth still have individual sovereignty and self governance as nations and only have to abide by certain laws passed by Colonial Alliance Parliament.
After NASA's successful first prototype of the warp drive in 2077 and the first successful test of a ship going to warp in 2090 humanity had spread all throughout the solar system and finally begun expanding beyond. As colonies in Alpha Centauri, Bernard's Star and Wolf 359 began to develop and grow it was decided upon in the United Nations that to ensure that Earth had power and influence in the future that the nations of Earth would have to cooperate together as a power instead of having the divided nations power dwindle as colonies would eventually surpass them in the future.
At the same time on the other hand Earth was very culturally and politically divided to where a global government was something the nations of earth would not accept to and wished to retain individual sovereignty. They realized though that they had to unite as a planet in some capacity to ensure Earths would continue to a great influence far in the future.
It was then in 2171 that the United Nations created the Colonial Alliance of Earth, a nation to represent Earth in space and unite colonies under its banner. Colonies inside the Solar System remained in the ownership of their respective nations on Earth but all extra-solar colonies that had been set up and all those set up in the future would be placed directly under Colonial Alliance governance.