Britannian Union
"We fight, we compete; evolution is continuous! Britannia alone moves forward; advancing steadily into the future. ... We will fight on, we shall struggle, compete, plunder, and dominate and in the end the future shall be ours!"
- -- Charles zi Britannia
The Britannian Union of Solar Energy
The Britannian Union of Solar Energy consists of both "New World" landmasses, the British Isles other than the land that constitutes Britain in the real world, Euro Britannia (a client state situated primarily in what would today be known as Turkey and Iraq), and the majority of holdings attached to the Orbital Elevator system. Prior to the One Year War, the Union was the largest voice within the Federation, bankrolling the entirety of its own Orbital Elevator and owning partial stakes in the others; it has also taken the brunt of spacenoid damage to the Earth, extracting heavy reparations from Zeon and even from other Earthnoid nations for this. Arguably, it still is the largest voice within the Federation; it is certainly the loudest.
Rather than rebuild the Americas after the One Year War, it took the money from those post-war reparations and moved many of its upper-middle-class and wealthy civilians into new habitations anchored to the Orbital Ring -- the so-called "Neo Colonies," boutique projects with outlandish shapes. Any wealthy Union citizen on Earth probably lives in the BU capital of Pendragon, in California, though the greater Nashville metropolitan area is also quite populous.
The Britannian Union also trends belligerent, bullying other Federation nations and even invading when the political situation allows. Invaded areas that stay under Britannian control become Areas -- stripped of their former cultural and political identity, reduced to a number.
Union holdings on Earth, save for a handful of large metropolitan areas, tend to be poverty-stricken, high-density habitations separated by large swaths of utterly nonfunctional wasteland. The Union does use Earth for military logistics, however; it formerly hosted the Federation's Jaburo base, and the Federation's current military headquarters, JOSH-A, also sits in Union territory.
It was the Union that advocated for both the Gundam Fight and the clauses that stipulated that the Earth is the ring. Union nations have won half of all Gundam Fights. It is speculated that these victories were what allowed these nations to funnel resources to their primary Neo Colony to escape Earth entirely.
During the pre-Federation era, Japan and the nations that became the Union were quite close. More recently, the Union took control of the southern half of Japan. As a result, there are still many ethnic Japanese in Union territory, especially in North America, Brazil, and the Neo Colonies (and of course, Area 11).