Not to mention the fact that English basically everywhere else but the US is essentially en-GB with a few choice changes and anachronisms. Consider en-IN, en-IE, en-SG, en-MY, en-AU, en-NZ, etc.

I started writing something a while ago with preliminary title “Do en and en-US, not en and en-GB”.

If you cluster English dialects by various characteristics, you’ll end up with en-US as a clear outlier. I believe that, if you’re going to divide English into two camps, the best is “English (International)” and “English (US)”. Canadian English is the one that’s closest to US English, but even it works at least as well based on International English as regards spelling (https://en.wikipedia.org/wiki/American_and_British_English_s... is an interesting read).

But there’s a lot more to it than spelling, and here the distinction is even clearer: the US has its own length, area, volume, weight and temperature units that no one else uses; its own stupid date format that everyone else loathes; its own paper sizes that no one else knows what to do with.

Not everyone else agrees on which date format to use, but we do all agree that any of our formats (DD/MM/YY, DD-MM-YYYY, YYYY-MM-DD, &c.) are better than the US’s middle-endian monstrosity. Though if we see the likes of DD/MM/YYYY we may mistrust whether it’s actually MM/DD/YYYY.

I also believe that you should default to English (International) for all users geolocated outside the USA.

Once you’ve get this divide right, adding further dialects also probably becomes quite a bit easier. But I do wish for diamond inheritance of locales: so you can mix in -ise/-ize, -yse/-yze, -re/-er, -ence/-ense, program/programme, and thereby deduplicate a fair bit across locales.

(There are still plenty of differences: such as time formats; decimal/grouping separators though I believe all places where English is a main language use . for decimal and , for grouping; even number grouping varies: en-IN does 1,23,45,678 rather than 12,345,678; keyboard layout; word choices; and lots more.)

(One last point: the naming is a bit fiddly. “Spanish (International)” means Spanish as used outside Spain. “English (International)” means the broad international/non-US consensus of what English is, generally following what England does but probably with kilometres instead of miles for long distances.)

I can’t find en-En…