[quote=@PrincessOfNothing]
Tbh, the Earth nationalities kinda felt anachronistic given the setting, but I kinda just went with it
[/quote]

I don't know that they have to. Nationalities are one of those things that people hold on to beyond reasonable levels--even if they weren't the same, I can easily see them being an identity that people hold onto even as they progress through the 'verse. As much as countries would cease to be quite as meaningful, I think it's just as easy to imagine the world holding onto it stodgy views of nationality even as they became closer to statehood than anything else.

And don't tell me you can't see the first Americans to set foot on Mars calling it the 52nd State.

Similarly, English actually is one of the more flexible languages, which would support its continued existance. It isn't necessarily that it's spoken by the most people so much as that it's substantially more adaptive within its own patterns than a great many others and in easier to learn than quite a few others not in that it isn't complex and full of potholes but because, as a language, English is very forgiving of mistakes.