I'm not arguing that it hasn't happened, Tequila, but rather that it's not a common thing. In some cases and instances the media has had a dramatic impact on US policy and discussion, but I don't think that they have the pervasive, controlling effect on a constant basis that some people think.
Not the media alone, I'd argue, but an aggressively partisan media in alliance with a political party/movement can drive polarization in a very strong and effective way. I also wouldn't argue that this is on a constant basis - but it is something we are unfamiliar with in the modern U.S. and a markedly negative development. Historical outlier or no, this is not a situatin which anyone growing up in the U.S. in the past 50 years is familiar with.