Comment by TulliusCicero

No London team even breaks the top 10 of most valuable sports team, but there are several US entries there, so that seems unlikely: https://en.wikipedia.org/wiki/Forbes%27_list_of_the_most_val...

I tried googling more directly for global popularity/famousness, but couldn't find any hard data.

And of course there's the issue of "has well known sports teams" vs "well known for their sports team". The former you could probably get data on somewhere, but the latter, I doubt it.