A while back, I was interested in this and looked it up myself. It's quite different from US systems.
In a few cases you see rabid fan loyalty, but the closest thing in the US would be college football. But you have to grow up in that environment (in Columbus, Ohio, there are only three seasons: training, recruiting and football season, Go Bucks!).
In the professional leagues, there is some resemblence to fan loyalty, but mostly fair weather fans (of which there are plenty in the EPL as well). However, the minor leagues get no notice and there is different interactions between the majors and the minors (compared to EPL and other soccer leagues in the world).
In the MLB, the major league club and minor league (Triple A) affiliations where they can send their players to get better or test them out. The NBA recently bought out the NBDL to try something similar. But it's never had any affiliation with the CBA or other pro basketball leagues (except the merger with the ABA). The NFL is the only league in town (merger with AFL long time ago) and Arena football is completely separate. I don't know much about the NHL with the minor leagues, but nothing like the EPL.
It's completely boggles my mind how one city can hold so many teams in the English leagues. I mean, we're not even talking about all of the UK, just England! Again, in Ohio, we have 11 million people and about 9 million root for the Ohio State Buckeyes in college. Sure, we have some other college teams in the top division (6 others), but we are
The Ohio State University for a reason
Yet there is a market for all of those teams in the EPL (it's actually Barclay's league or something). So many
suburbs have teams! And the fact teams can get relegated and promoted from one level to another is just wild. For someone who grew up with it, that's normal. But from the American perspective, it's completely foreign!
In the US, that would never happen in any of our current leagues. The MLS itself is radically different in its design. The most popular sport (football) is 'maxed' out at 32 teams and chances of expansion in the future are slim-to-none because none of the owners want to split the revenue. Chances of being relegated would just be unthinkingable.