Part (or the whole?) of the problem is the amplifier isn't reaching the "rest" of the country, but rather selectively isolating who does and does not receive the message. Newspapers were visible to all. When I pick up a broadsheet to read I know that I'm choosing a particular source of information; and choosing not to read a different source. But I'm aware that there are other newspapers and that knowledge influences how I weigh what I read compared to what other people are reading.

Two people who live near each other, work together, shop at the same stores, send their children to the same school, et al, will have completely different experiences when they go on the internet. And each person's experience is hidden from the other, so there is no way for one person to get a glimpse of how the other is seeing their news. That means if those two people were to talk to each other about what they've seen on the internet, they will be confounded by the lack of common experience. What shared experiences exist are likely banal topics such as sports or movies. Each person will be convinced that their knowledge is the dominant viewpoint because it's the majority of the things they find on the web. It's the other guy who is missing the big picture.

Instead of me choosing the newspaper. It's the newspaper choosing me.