My sense (as a Japanese expat) is that the smaller and closer to China the country is, the more serious people there are thinking about moving out of the country as a risk management, encouraging them to learn English harder. Another good example is Taiwan. It has a lot of good English speakers in its highly-educated cohort.

Japanese people aren't that serious about moving out (at least my generation. Your people look a bit different though.)

That breaks down as soon as you leave Asia. In Europe, most people attribute it to whether the country prefers subs v dubs. SK and Taiwan use subtitles for foreign media so they hear English language. In Japan, it's more common to dub.

This is mirrored in Europe where countries using subs (Norway, Sweden, Netherlands, etc) have better English language skills than dub countries (France, Germany, Spain).

Yeah. Horrendous Japanese English has to do with what I'd describe the "software" approach. Japanese English textbooks is written like a programmer's manual that grant readers a means to generate or analyze English scripts in certain punctual grammatical ways. IIUC, most other Asian nations including SK don't take this approach at all, and their English proficiency is massively higher.

I'm not sure if any other countries than Japan do that, but I smell something similar might be going on in public education in rural China; it's a somewhat usable alternative where immersive training is not available.