Mass media homogenizes our input (which influences our output). If we want to think about how AI might be different we should consider how it might directly homogenize our output.
Mass media are not only able to deliver the same message to everyone, or the same presuppositions to everyone (a more dangerous thing, as the desired conclusions are then drawn by people themselves; see Bernays's "music room" tactic for getting people to buy pianos), but once the same content has been delivered to everyone, people will talk about it at some point. This creates the impression of consensus which causes people to assign greater confidence to the content that the mass media have delivered.
So it's circular. You put an idea in people's head, they all end up talking about the idea, and this causes people to feel confident about it being true, because everyone is talking about it. And even if you don't consume mass media, you still face a society of people who do. You don't escape the effects of mass media simply because you personally don't consume it.