You raise a great point here. At what point will a non-English speaking country become the nation with the most English speakers? In my mind, surely that is Indian by 2050. If they can become upper middle income by that time (I am sure of it), then I guess more that half of adults will speak English at least at elementary to middle school level. (Dear reader: Please don't read that as a slight against the English language skills of Indians. I know from personal experience: With five grade level language skills, you can get a lot done!) They would way out number the number of English speaking Americans.

I'm in IT right now having travelled through FR, DE, NO, PL and half a dozen more countries. When selecting the EN option on a website it is almost 100% of the time with a GB flag. The spelling is mostly en-GB as well.

In this case, Japan is special. There relationship (post WW2) with the US is unparalleled compared to France or Hungary. It will absolutely be US style. Japan was never very close with the UK.

Correct, generally speaking they will have their own default locales on their computer and local sites will be in e.g. French but going to Instagram it will render in US English - unless the app has been translated, which it probably has so it's not the best example.

> not Indian English, not Chinese English

There is no such thing as Chinese English, unless you politely mean "English as incorrect spoken by Chinese native speakers."