The Syndic (Sci-Fi Classic). Cyril M. Kornbluth

A future North America is divided between rival criminal gangs the Syndic on the East Coast and the Mob in Chicago, who have driven the federal government into exile in Iceland, Ireland and other North Atlantic islands. Life has more or less returned to normal in Syndic territory – as long as protection money is paid on time. The rest of the world has collapsed into either peasant life or tribalism.