Name of user language, in English

Does Juce have a function that is able to report the English name of the user’s language?

I studied the LocalisedStrings class but didn’t find a method for querying the system’s user language setting.

No, the LocalisedString stuff doesn’t really know what language it is, it’s just lets you give it a translation table to use. I suppose you’d need to call a standard C locale function, though have never tried this before.