What changes to history needs to be made so that once the 1900's roll around with industrial wafare and global wars, there are 6 major world powers, one based in each continent (Europe, Asia, Africa, North America, South America & Oceania).
The biggest difficulty I see here is making sure there's only 1 European major power, that doesn't get it's strength from a large overseas empire, perhaps something akin to a surviving Rome or centralized HRE.
An African major power also seems difficult without a major early PoD, what would be the best candidate there?
What major powers do you see as likely canidates?