Japanese authors trying not to mention something about their country somehow in any manga/LN : Challenge level - Nightmare Difficulty
seriously, imagine the author being from the USA and calling it America or from the UK and calling it Britain. It's really cringy.
I don't think I've ever read an isekai where the Japanese protagonist comes across another isekai'd person that's not from Japan. You'd think in trying to be realistic in that with how big our world is that other isekai'd people would most likely be from other countries. I don't know why they never explore that, if anything it could add more to the story and characters.