Probably gonna be france, but hat's off to considering Britain. I mean I don't get the point in having your most used mascot on top of the most famous French landmark starting off a trailer for a game which has very Parisian architecture in a city that features a huge Eiffel Tower like structure, only to give us Britain of all things. You do that not as a red-herring, but to get people thinking of what a Paris based region can be like. Not to mention, the Manga site has some French Adventure thing, and Masuda has been in Paris for a while a couple months ago, being super happy about it and what not.
Also:
https://en.wikipedia.org/wiki/Palace_of_Versailles
The Palace of Versailles. Almost exact same architecture for that palace, and the huge water body with a bridge is strikingly similar.
https://www.google.gr/search?q=pari...QMenW0QXamYDYBA&ved=0CEMQsAQ&biw=1280&bih=911
Take also a good look at all these buildings, compared to XY. Kinda the same vibe going on right? You know why too, right? Yes, because its based on France!