Three channels (at least 3 networks) on TV. Perhaps more than one local paper, but all the out-of-town news came from UPI or AP. Time and Life. Maybe the New York Times. And that was about it. Those eight organizations defined mainstream culture. And their positions were not very far apart.

Nothing has that level of control today. There are more major organizations, and they have much more divergent positions. As a result, the culture has fragmented, becoming multiple cultures. There is no "mainstream" any more. There are multiple major streams, but no one mainstream.