The Premier League has contracted four times in the past couple of 23 years, and is making more money than ever. The wider the audience for a league, the more important the big teams become, and the more discardable the bottom-tier teams become.
That model makes sense for a country the size of Louisiana. You have, for all intents and purposes, a three-team league where 2 of the teams play in London and the third in by far and away the next-largest city. No matter where you live, you are never more than 300 miles from a championship contending team.
This would be like the province of Quebec having its own elite major hockey league, where the championships are always won by one of the teams in Montreal or QC. Everybody else is there to play the role of Washington Generals. Naturally, those two highly elite teams are going to be marketable and make a ton of money. Whether Val-d'Or has a team is trivial. Relegating scrub teams is an afterthought, because the fans in those towns will still follow the league passiontely.
But in the United States, you're not going to make tons of money in a league where only New York and LA win championships. People aren't going to follow a team that plays 1500 miles away. In order to make the league viable on a national level, each major population center needs to be represented by a team -- and
that team needs to be good enough on its own to survive financially. Whether they're relegated to the "minors" or simply scrape rock-bottom for a decade straight like the Islanders doesn't matter. If the team isn't relevant, it won't sell, and it will lose money (unless it has the good fortune to be the Leafs or Knicks). That means the league fades from view as well, as entire cities get turned off of the product.
Yeah, you'll still sell tons of jerseys for the NYC and LA teams. Yeah, they'll probably get good ratings in one-off events like the championship game or a New Year's matchup. But generally speaking you'll be running an extremely unhealthy league where the majority of teams are constantly on the brink of failure. Never mind the legal and practical barriers.