system
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human
ELI5: In US sports, why is it that there aren't tens of teams per state/city...like in European football?

I'm just wondering why in sports like basketball and football, which seem so popular, there aren't so many teams like they do in the UK, or perhaps? Is there some kind of law that prohibits this? Thanks for your answers. 

Edit: Thanks a lot guys! Really some wonderful answers here. I am a football (soccer) fan myself, never really enjoyed watching any other sport. I mean, in football... when i was a kid, i found it very creative and interesting how 11 players have to go against another 11 players and figure out to put the ball inside each other's net...and using mainly their feet. It takes skil, a lot of timing,l and A LOT of teamwork to pull that off.

Until...i watched this rerun of some NHL game on TV the other day. I just couldn't stop watching. I just think it's impressive how you have to put that little black puck (as opposed to a ball) inside that little goal (Google tells me football is almost 24 feet wide, NHL is only 6 feet wide)...all the while SKATING ON ICE?! I mean....shiieeat!! And the speed at which everything seems to happen is too much. Oh yeah, since you're on skates...i'm guessing you don't get to ever stand still either? I've noticed everyone just keeps moving to just keep the momentum going (but that's just an observation from one game).

Which brings us to why i started googling furiously about this sport. Which is when i got to things like "minor leagues", "franchises", "drafts". I said screw it. I need someone to explain this to me like i'm five.

And btw, I appreciate the fact that they have salary caps in American sports. I wish they had that in European football.

You guys have been great! Thanks!!
gpt
Put simply, its because we have different approaches to organizing sports leagues.

In the US, most major sports only have one major league (NFL,NBA,MLB and so on) which can only have a certain amount of teams. When you consider the vast distance between most US cities, it makes sense to spread them out a bit so that more people will have one within a reasonable distance.

In the UK (in football at least) we have a multi-tiered league system with literally hundreds of teams. Unlike the US leagues which are run as businesses with a franchise model, any group of people in any town or city can start a team and enter it into the football league system if they wish. With this openness, it can hardly be surprising that a place like London has more than one team (heck, even if they just had one team for each borough, they could fill out the premier league on their own).

**TLDR;** The (English) football league is mush more open to new teams, thus more teams.