The FCC regulates all 3, but they have a lot more control over OTA content because the electromagnetic spectrum doesn't have enough room for everyone who wants a TV station to get a channel. As a result, if you do get one, it comes with strings attached and you have to serve the public good as well as whatever else you want to put out there. In addition, a broadcast is out in the open, blasted out in all directions for anyone with a receiver to see and hear, so much like being outside means some of the things you can do in private are not allowed, TV networks can't broadcast some content that is otherwise legal. Those constraints offset some of the first amendment protections that would otherwise exist.

Cable and internet don't have these properties. They're constrained only by how many lines of cable you can deploy in an area, and physics isn't stopping anyone from running their own. And since it's not being blasted out into the air in all directions, it's closer to private communication. Without those justifications, the full protection of the first amendment still applies.