Sorry, but this solution doesn't work (at least for me).
My language setting on Apple ID was already set to English (US). I switched to other language and came back to English, and nothing happened to iCloud.com (web version).
In my Apple devices, language setting kept English as desired.
Since iCloud web was updated, the language setting is missing. Maybe it's following browser settings, maybe it's following PC settings. Anyway, I'm very upset with the lack of this simple option.
I believe the only solution will be to wait Apple decide to re-include language settings on iCloud.com (as I'm waiting for a web version of Freeform, to not mention an update on Find My's web version layout).