I've read that his own language (Prussian) pretty much died out in the 1800s and there are a few pockets of communities in Europe trying to revive the language today, but I'm not a Germanic history buff so I'm still guessing.
Maybe he fully speaks and thinks in German, or perhaps he thinks in Prussian and speaks in German, as way of reminding himself when he was fully 'awesome', so to speak.
I suppose it could be possible that as a 'dead' nation his accent is stuck as it was in 1947, which could be rough, Prussian accented 1940s German. Or maybe his accent has become modern along with the other nations?
Does any Prussian and German dialect sound similar? Am I talking out of my butt?
I'm not planning on writing a story about it, I'm just curious and wondering what everyone else thinks.