I know it's not black, but I really liked how Daisy had a darker skin tone in these LINE stickers and Mario Tennis and wished that they used it for the jump to the switch. It's a bit sad that it didn't happen, because it's just something slight to make the cast more diverse without having to create a new relevant character, and it'd make sense for her, coming from a desert kingdom.
At the same time, I think that maybe the push for more black people/diversity is just something that's more clear to see in North America than in other countries, specially Japan. I suppose if NoA had more to say on the bussiness, things would be different.
In Europe we have many african inmigrants and I guess it'd be nice for them to get more representation so that they feel more included in society, but normally when I read about diversity it feels to be focused black-american people.
Which... I guess makes sense in an English forum, uh.
The only characters I can think of that are specified to be from America are Little Mac and Solid Snake, but maybe talking about this is missing the point, as those fiction kingdoms could have been created to have fictional diverse people too.