I think you misread: most of mainland Europe including Germany use dd.mm.yyyy or something else that is reasonable sane even if it isn't sortable like yyyy-mm-dd. Or am I wrong on this? Norway at least use mm.dd.yyyy and never mm/dd or mm.dd.yyyy

Afaik Norway also uses the sane format: DD.MM.YYYY

See parent source: https://en.wikipedia.org/wiki/Date_format_by_country

Edit: of course. To late to edit but if you read my post, but that was what I meant.

Schools still teach DD.MM.YYYY. That’s what’s relevant because that’s what people actually widely use.

Shouldn’t Americans be very familiar with the idea that official norms (the metric system) play no role if the people don’t want to use them?

I understand - it seems I was too optimistic to read that the use of yyyy-mm-dd has become "the official standard" in Germany, without considering the popular usage and convention under discussion.