Over the past five years, every industrial nation has had its own version of the same economic fight: champions of austerity on one side, advocates of social spending and economic stimulus on the other. It’s tempting to view America’s ongoing political dysfunction as merely one version of this fight, and thus to dismiss it as an aftereffect of the 2008 financial collapse. But the peculiar form the fight has taken in the United States — threatening every few months to hobble the economy with a government shutdown or a debt default — suggests that the country’s institutional dysfunction is no longer…