Rather than separation, it would be consolidation. In a way there's a few real world analogs that might be a useful starting point. Rather than superstates, this would be confederations of mutual self interest.
The EU is already in a bit of a period of political and military unity and spreading outwards peacefully. Eastern Europe's been wavering between russian and european spheres of influence and this might bring them into conflict with the Russians. Give them an ultra nationalist government which loses the war and their opponents might partially ally with Europe. In an attempt to 'help' an old ally, the Chinese might invade the far east forming a second superstate.
A militarily strong china would be scary for much of Asia, and they might band together to form a third superstate. A loose "Asian Confederation" of sorts.
Now, Britain might not want to be part of the great european commonwealth. They might ally with the US, and Canada forming an atlantic alliance, along with former british colonies and maybe bits of Russia. Australia and New Zealand feel like a natural cultural fit here.
That leaves South America and Africa There's probably parts of Russia at this point that still believe on socialism and they flee. Starting at places with natural inclinations towards socialism, say Venezuela, Bolivia and Angolan, they unify into a new 'USSR', and invade and retake chunks of old Russia.
The middle east has run out of oil and is kind of unimportant. Its a land of dust general unimportance. No one cares particularly about it outside being neutral ground, and some tourism. Its probably the place where intrigue.
So, why socialism for South America and Africa? They're resource rich, industry poor. And while communism is a terrible idea, it was made worse by people. Have resources controlled centrally by computers and it just might work. It would also allow for the 'state' to centrally manage industrialisation and to kickstart their economies. A 'natural' rivalry between them and the 'Atlantic Alliance' due to the russian and south american elements, and the african elements being courted by china would be handy too.
The expanded chinese government might not be the communist party at that point, but would be sandwiched between European Russia, and an american buffer zone. They can't retreat due to strategic reasons, but its an uneasy territory. Getting invaded by the new USSR might be a interesting way to move the story, especially if you have a 4 way cold war.
The asian confederation is sort of neutral. Unlike the other states, they have no natural enemy (other than the Chinese, who are busy with the Atlantics, Europeans, and Soviets), and are kind of following their own agendas. The Indians and Pakistanis don't quite get along, ASEAN has been their own little club and wants better economic ties with everyone, the Japanese are still wavering between pacifism and hitting the Chinese pretty hard when they aren't looking, and so on.
I'd like to think the atlantic alliance is isolationist as far as terran affairs go, but they're trying to beat everyone, since they've had a lot of experience in space.
Of course? Why? We're out of oil of course. helium 3 on other planets! Martian Iron Mining! Massive space platforms! Other cool things! Space battles!