How Did We Become This Divided?

After 244 years together as a nation, we seem to be growing apart. 80% of Americans now have few or no friends across the aisle. In a poll before the last election, 15% of Republicans and 20% of Democrats agreed that the country would be better off if large numbers of the opposing party just died. Outrage in America isn't new; what is new is how much money entire industries are making off our outrage.