Cory Doctorow is talking on his excellent Pluralistic blog about the collapse of AMC, and the monopolies involved in it.
What's more, AMC took advantage of America's nonexistent antitrust law to buy most of its competitors, making it the only screen in town for many of America's cities.
AMC's demise matters, then, because it constitutes the bulk of American screens.
This is going to be interesting how the movie industry is going to look like in a year or two. AMC is dying, and Disney now has Disney+ and could just release the bulk of it's movies there. "Trolls World Tour" was a raging success and "Artemis Fowl" is going to be released exclusively on Disney+ too.
However, Time-Warner are cutting into Disney's profit (not that Disney isn't still making truckloads of money though) there:
So Disney needs big screens, especially since its Plan B, streaming media through Disney+, is being demolished by Time-Warner/AT&T;, which is using Trump FCC Chairman Ajit Pai's obliteration of Net Neutrality to upcharge customers who choose Disney+ over HBO Max.