It's the US legacy media that is the main reason for the polarisation - the two party system is a factor, but the regular media is the one pitting "us vs. them" in every single minute of every broadcast.
Social media has downsides, but to lay the blame firmly at the feet of Facebook is to willfully ignore the culpability of CNN, Fox, the NYTimes, Washington Post, and many other legacy media outlets that are making tons of money otherizing the part of the country that is not their readership.
Social media has downsides, but to lay the blame firmly at the feet of Facebook is to willfully ignore the culpability of CNN, Fox, the NYTimes, Washington Post, and many other legacy media outlets that are making tons of money otherizing the part of the country that is not their readership.