Also sprach wiki:
The Britannia royal family starts from a Celtic king who resisted Julius Caesar’s invasion of Britannia, which led to the creation of the Britannian Empire. This divergence in history causes many other differences: the retaining of absolute monarchy, the suppression of the American colonies' rebellion in 1776 and the conquering of the American continents. Its calendar is "Ascension Throne Britannia", or a.t.b and also know as the Imperial Calender in the English Dub. It remains in expansion, with the recent invasion and colonization of Area 18. Britannia invades Japan to obtain a newly discovered energy source, the Sakuradite. Its ideology is based around social darwinism.
Its homeland itself is based on North America, with additional territories spanning the western hemisphere, including the rest of the Americas and Greenland. It also controls New Zealand, Japan, and parts of the Middle East, though the status of the Philippines is not clear. It notably does not have the British Isles themselves, having lost them to Napoleon. In total, it controls over one third of the world's population.
The E.U. was born during the time of revolution (1800s). Unlike the Holy Empire of Britannia, it is more democratic and supports equal rights. It has long been in conflict with Britannia, with a legendary commander stationed at El Alamein checking the Britannian advance into North Africa. It encompasses all of Europe (including the British Isles), Russia, and Africa.
The E.U. apparently organizes their military into left-wing and right-wing camps, and their forces are drawn from National Guard-style units from a member nation (i.e. the German National Guard, the Italian National Guard and the Dutch Engineering Corps).
So on the plus side we eurofags have the rori council, but also the Renault mechas.