> France was historically always focused on Paris, because that was where the Emperor was.

So much misconception in such a short sentence…

First of all France only had an “Emperor” for a few decades (10 years for Napoléon 1er, 17 for Napoléon III).

Then, Paris wasn't even the King's main residence for a good part of French Monarchy (the Loire valley (hence the list of famous castles here) and Versailles both aren't Paris).

Centralization around Paris built up progressively, but it's really the French revolution (which came with the suppression of the old regional Parliaments) which made modern France the way it is. And the US is the only place where you can claim that 200 years of history counts as “always”.

As I said in a comment sibling to yours, this has nothing to do with political organization, it's a consequence of demography: French people just stopped having babies one century before other European countries (and two centuries before the rest of the world).