Truth be told, the Roman Empire wasn't a Christian nation when the precedence of sees based on the importance of the city they occupied was begun, but Rome ranked first as the capital, even when Diocletian was adorning the Church with martyrs and defiling his soul with violence, even as Alexandria ranked second as the second most important city in the Empire, and so forth.
Like it or not Washington is the capital of the Empire now. And I use that word without prejudice--post 9/11 I decided American imperialism is a good thing.
The center of today's Orthodox world is in Moscow, like it or not. That's where the EP should be.