He has crossed the Atlantic and he's well known... if you follow/know basketball.
LeBron/MJ/Shaq he's definitely not, but Americans I'd wager mostly know him - he's in the NBA hall of fame and had a pretty impressive career as a player, and a pretty meme career as a coach so far. It seems to be on all the American sports outlets/sites, even more so the Texas/Dallas ones - as I mentioned, I'm a Mavericks supporter and this is all over the news. It's decent exposure in a rather big "market", as it will generate interest, but even then everyone's just mentioning it and asking the same as us - "but why?"
I assume he's a 1% "investor" or something similar with no power over anything obviously. I also assume we'll see a lot of Dallas Mavericks cross-marketing in the near future.