The US is likely decades away (more specifically, it's loot boxes that are a problem, rather than MTX themselves). It will depend on how hard companies push the envelope and whether it becomes a societal problem (which would then takes years of studies). Given the direction of sports betting, It's more likely we're heading in the opposite direction.
It's up to the consumer whether they want to pay $60 + dump additional money into their account.
They can download League of Legends for free & optionally buy characters & costumes.
At this point 2K would probably be better served going the FTP (free-to-play) route, but they can't because they don't own the IP. The only reason we're still buying the game is the NBA's billion dollar licensing fee.
MyTeam is a gacha game. I'm curious how many players actually know what those are and realize they're playing one. 2K certainly hits a different demographic. Just as there are lots of people that dislike RPGs like Final Fantasy but then play MyCareer.