the mind boggles! inventing 2000 years of 'new' history has got to be a mammoth task! more recent 'what if's' would be easier for sure
i think one single power ruling the world is more science fiction fantasy than a real possibility, and as the global population shoots up, it gets even less likely
the evolution of philosophical thought means that the old religions would have died anyway, regardless of how they were replaced
but it could have meant no christianity, no islam, judaism destroyed, no renaissance and so on...
latin might have survived though