I think the Tory/Labor division that existed in the newspapers, and the way that dynamic changed in the Rupert Murdoch era (https://en.wikipedia.org/wiki/Rupert_Murdoch#Activities_in_t...) should be studied in light of emerging polarization you're discussing in the US. Creates a self-reinforcing news duopoly that is very persistent and harmful. I suspect that as people look back on the end of Great Britain that we are living through and how it has fallen as a global power it will be interesting to see how media driven internal division was a factor.