Inspired by someone's effort to map the world of the Code Geass anime.
This TL diverged in the early modern era, rather than Roman times (the dinosaurs survive in South America, the Roman Empire survives, and President Nixon is elected president of the US in 1972. That's the original's historical plausibility).
The British monarchy being more successful in maintaining its power in the face of Parliamentary challenges. In the early 1800s, a Napoleon-analogue drove the monarchy into N. American exile
Its the year 2009, and the Brittanian Empire has established a Decades-of-Darkness-ish dominance over the western hemisphere. Areas not directly incorporated into the Empire proper (due to an overabundance of dusky-skinned inhabitants) are run as the eighteen Control Zones, essentially colonies, although the whiter locals are allowed to assimilate into the ruling class.
The Empire is essentially fascistic, militaristic, racist and hierarchical, although the Imperial Party and the First Chancellor nowadays are more powerful than the old nobility (many of which, however, are high members of the party) or the mostly figurehead monarch. Various small wars are always being fought to maintain order in the Latin American Zones, but the Party sees this as a valuable toughening experience for young conscripts. The Brittanians have the worlds most powerful military, and being quite capitalistic, have a fairly strong economy as well, although paranoia and censorship tends to hurt them when it comes to high-tech development. The nigh-omnipresent uniforms are snappy: their competitors grudgingly admit that while the Brittanians are bastards, they are bastards with some style.
The Britannians dont really get their competitors, or why the French, after achieving close to a European hegemony in the early 19th century, failed to follow up by turning Europe into a centralized imperial state. The eventual transformation of Europe into a loose French-headed federation, and the withdrawal from colonial control in Africa, strikes the Britannians as insane, and they mutter about European weakness and degeneracy.
Still, they generally don't go so far as to put their money where their mouth is: Europe is wealthy, well armed, and is the world leader in technological innovation. Also, despise each other they might, but Europe and the Americas do engage in quite a bit of trade. Europe is the center of world democracy, and the Imperial Union of France, Ireland, Northern Italy, and various other bits is nowadays a parliamentary monarchy, albeit one with somewhat uncomfortably strong security services and universal conscription. It has a number of allies, including Russia and the Ottoman Republic , which get along about as well as NATO members Greece and Turkey in our world.
Russia is nowadays a republic, and is populous and wealthy enough to be a near-superpower if not quite on the same level as the European Block or the Brittanians, but it has a long border with the third great power, the Chinese Imperial Federation, and feels safer with the Europeans firmly in its court.
China, which opened to the west and began seriously modernizing earlier than OTL, is considered a bit backward by the other powers: through sheer bulk it operates on a comparable global level, but internal wealth disparities are enormous, the pollution is dreadful, and its multiple 10-million plus cities awe and somewhat horrify foreign visitors. Much richer than our China, it still suffers from food shortages due to pollution and desertification, and although nobody starves, the synthetics and vat-grown stuff eaten by some of the poor is unappetizing at best (the Chinese government is very leery of becoming dependent on food imports from either of the other great powers). Said government is somewhat undemocratic, with a weak and wealth-dominated parliamentary body, often overmatched by the Emperor and the enormous bureaucracy. (Think turn-of-the-century Imperial Germany, although with more decapitations). Still, China is a massive weight on the international scene, a global workshop and forge, producing more electrical power from atomic energy than its two competitors combined, and has never suffered national humiliation on quite the level that OTLs China suffered from the Opium Wars to the Japanese invasion.
India, never fully colonized by Europeans in this world, is divided between Chinese and European allies, and the Hindustani Confederation, which wants to see a united Hindu India, spends a lot of time muttering about foreign conspiracies, although theyre intelligent enough not to touch Brittanian alliance offers with a ten-foot pole. Africa, decolonized later than in our world, is still a bit of a mess: for one thing, in this UN-less world, if African dictator A wants to nab part of Dictator Bs country, there generally isnt too much fuss. What there is fuss about in Europe is the increasing Brittanian influence in Africa, as local rulers are bribed into giving basing rights, exclusive contracts, etc. to Brittanian agencies, governmental and otherwise. Outright establishment of puppets or military intervention is still considered a no-no due to the hostile attitude of Europe, but the Brittanians are always pushing the boundaries.
Beside the three big power blocks, there are three important middle-sized neutral powers. Iran is a nuclear armed, industrialized state with a standard of living relative to the European nations comparable to that of our South Korea vs the EC. It also has a turbulent multi-party political system, Prohibition, and a labor shortage due to rapidly slowing population growth that is leading to what many politicians and TV pundits claim is a flood of uncivilized immigrants from the kingdom of Arabia, Afghanistan, and India. Nieuw Holland, which the Dutch colonized earlier than the British OTL, has 40 million inhabitants, nuclear weapons, and a lot of attitude, as well as being the most extraordinarily efficient water-users on the planet.
And then there is Japan. Modernizing no earlier than OTL, the Japanese were never strong enough relative to China to successfully pull off a land grab, although they managed to avoid becoming vassals or outright absorption like under-populated (at the time) non-Viet SE Asia. In this world the Japanese are known for political agility and making-ends-meet practicality rather than militarism or pedo-porn, and have managed a certain proud autonomy in a world of giant powers. Poorer (relatively speaking: the world is overall a bit wealthier than OTL) than our Japan, they are still a first-world country.
However, the Japanese have found themselves, much to their unhappiness, the center of world attention, after seismic studies for a possible mine uncovered a 3-mile long spindle-shaped object lying half a mile underground. After excavation confirmed yup, an alien spaceship, the entire world clamored (with some shaking of atomic weapons) to get a look in. After discussing the possibility of just blowing up the ship with a big nuke and trying to forget it was ever there, the Japanese government agreed to give access to all the major powers: but only under close Japanese supervision, so anything written, taped, put onto computers, etc., would be fully accessible to all the other powers plus Japan, and nothing but information was to leave the spaceship.
Not unsurprisingly, the situation has become a paranoid nightmare, as everyone tries constantly to cheat and scientists terribly pressured by their governments to produce results must deal with constant monitoring and the somewhat sketchy living conditions inside a crashed and still not fully excavated spaceship . And always there is the constant fear that somebody will figure out something that nobody else has, that will give their nation a fundamental advantage and then proceed to nuke the hell out of the spaceship, which is quite close to a densely populated area.
In fact, both the Japanese and the Britannians have already made some very interesting deductions...