The changes weren’t just local. The George W. Bush administration four years earlier had used Sept. 11 — another calamity — as a pretext to strip Americans of their civil liberties, to conduct a pair of wars that were themselves humanitarian, diplomatic and economic catastrophes, and to amplify its own authority. In fact you can see the administration’s response to Sept. 11 as a struggle primarily not to subjugate terrorists or battle distant regimes, but the American public. It did so by instilling fear, chipping away at rights, demonizing Muslims, expanding its powers and using wartime ideas of patriotism to quell dissent. The failure to prevent the Al Qaeda attacks could have discredited the regime; the regime was trying, as regimes often do, to shore up its authority.

That authority came crumbling down with the administration’s callous and incompetent response to Hurricane Katrina, particularly to the stranding of New Orleanians, mostly poor and mostly black, in their flooded city. (Two days after Katrina hit the Gulf Coast and put 80 percent of New Orleans underwater, Bush said, “I don’t think anyone anticipated the breach of the levees,” videotape of him being warned of that possibility a day before the catastrophe later hit the media.) The outrage over the response undermined the Bush administration’s mandate to govern. “Katrina to me was the tipping point. The president broke his bond with the public,” Bush pollster Matthew Dowd said. “I was like, man, you know, this is it, man. We’re done.” It ended the post-Sept. 11 era of deference to this particular authority — and some argue that by exposing the festering racism in American society, it strengthened the case for electing a black president a few years later.

“This is our Chernobyl,” a doctor in New York City said recently. He seemed to mean that not only were medical staff front-line workers in grave danger, but also that institutional authorities were in the process of failing civil society, as Soviet hierarchies all the way up to the Kremlin did in the 1986 disaster of a nuclear meltdown that spewed radiation internationally and contaminated hundreds of square miles of Ukraine for millenniums to come. The man at the top of that hierarchy, Mikhail Gorbachev, reflected years later: “The nuclear meltdown at Chernobyl 20 years ago this month, even more than my launch of perestroika, was perhaps the real cause of the collapse of the Soviet Union five years later. Indeed, the Chernobyl catastrophe was an historic turning point.”

Managua, Nicaragua, in 1972 and Mexico City in 1985 both suffered major earthquakes after which the corrupt and venal government response prompted long-term change. The Somoza dictatorship seized more powers in the wake of the Nicaraguan disaster, but in so doing it strengthened the case for the Sandinista revolution that swept it away later in the decade. In the wake of the quake in the Mexican capital, made worse by corruption in the enforcement of building codes beforehand and in the distribution of relief and rescuing the trapped afterward, public dissatisfaction with the one-party government boiled over. (In one instance, the police provided support for a sweatshop owner who wanted to rescue his equipment from a collapsed building but not the seamstresses trapped inside; this concern for property and profit over human life is often one of the flash points for ensuing political conflict.) A seamstresses’ union, a housing rights movement for the displaced and challenges to one-party rule were among the results.

Disasters test regimes. Some fail the test. Incompetence, indifference and self-interest are easy to see in the stark light of an emergency. People whose lives have been thrown into turmoil are no longer cautious or deferential, and no longer accept the inevitability of a status quo that is already in disarray. Things that seemed impossible have already happened — in our case, much of the economy has shut down, much of the population has suspended its ordinary activities, and sweeping new social programs (canceling student debt, for example) suddenly seem within reach.