That's actually cool and a bit like what I had in mind. But it doesn't seem to offer an actual hierarchical view of the lemmyverse.
It would be nice to have a forum style clear treeview of the forums (instances) and their subforums (communities) with activity indicators etc to make browsing and discovering content straight forward. Then if you subscribe to a community it would also show in it's own treeview that the user could arrange to their liking.
Wouldn't it be more correct to say that most Americans also use a messaging app (iMessage). The rest are just stuck with SMS to have compatibility with the iPhone users.
As the iPhone was (is?) not as popular in the Europe as it was (is) in the States that might also be one of the reasons why people here ditched SMS so fast once smartphones got popular.