> Here's a list of the Windows locales:
> <https://www.science.co.il/language/Locale-codes.php>.

Just for English they have all of these:

English - Australia         en  en-au
English - Belize            en  en-bz
English - Canada            en  en-ca
English - Caribbean         en  en-cb *
English - Great Britain     en  en-gb
English - India             en  en-in
English - Ireland           en  en-ie
English - Jamaica           en  en-jm
English - New Zealand       en  en-nz
English - Philippines       en  en-ph
English - Southern Africa   en  en-za
English - Trinidad          en  en-tt
English - United States     en  en-us
English - Zimbabwe          en  en-zw?

So using a locale with both language and country would make sense.

The Caribbean country code (cb) seems like their own invention;
"Caribbean" is not one country and I can't find a "cb" code in ISO for
any country. Not sure what to do about cases like this. Maybe the WinAPI
error wrapper can just provide en-cb even though it's unofficial, and
people who know t and want it can ask for it.