It’s a shame that they aren’t more popular; I didn’t really see prefectural flags flown that much outside of government buildings when I lived in Japan.

I’m not a lawyer and I’m not from US, but I’m pretty sure this is not how it works.

Ah but it is. The US is, as far as I know, the only country who taxes its citizens who are living abroad. And yes, it is as stupid and shitty as it sounds.