More seriously, this world would actually be closer to the 'Batman, Holy Terror' framework, rather then the 'All-Star batman'. Just replace Great Britain with the Brittanian Empire and dole-up the outfits a bit and you have a pretty good match. How Cassie and Stephie fit in exactly is anyone's guess (though they'd probably be a lot healthier), but it still fits better in terms of Batman being an urban legend rather then accepted figure who Bella has never been exposed to, the lack of anything resembling a Justice League, and of course the fact that America has been conquered by a hostile power.

Actually, that has some pretty chilling implications, once you consider Cassie and Sagara, then you consider all the people who really seem too young to be pilots and soldiers in Code Geas.