Letter four

James Naughtie reflects on the causes and consequences of the polarised politics of the United States. Looking back on 50 years of American experiences, he explores the conservative revolution that began in the 1990s, the culture wars that brought a sharp partisan tone to every public debate, and the resulting challenge to the system of government itself. A modern American revolution, played out in the years from Bill Clinton to Donald Trump.

Produced by Tara Neill and Regan Morris for BBC World Service.