VENEZUELA, WHICH was once Latin America’s richest country, has become an unwilling test site for how much economic and social stress a modern nation can tolerate before it descends into pure anarchy. This month its 31 million people lurched a big step closer to that breaking point, thanks to another senseless decree by its autocratic populist government.

For years Venezuelans have struggled with mounting shortages of food, medicine and other consumer goods, as well as triple-digit inflation that has rendered the national currency, the bolivar, worthless. By this month the 100-bolivar bill, the largest note in circulation, was worth only 2 cents, forcing people to carry piles of them in order to make the most rudimentary purchases. Then came this coup: On Dec. 11, President Nicolás Maduro, an economically illiterate former bus driver, announced that all 6 billion 100-bolivar notes would cease to be legal tender in just 72 hours. He also closed Venezuela’s borders with Colombia and Brazil, on the theory that traders were hoarding currency in those countries.

Almost overnight, millions of Venezuelans — about 40 percent of whom do not have bank accounts in which the currency could be deposited — lost the ability to purchase even those goods still available on the market. The result was predictable: looting and riots in at least eight cities. In the eastern town of Ciudad Bolivar, with a population of some 400,000, hundreds of stores were looted and at least three people were killed in three days of mayhem.

Mr. Maduro was forced to modify his fiat, extending the currency’s validity to Jan. 2 and reopening the borders. The government says it will distribute new bills in larger denominations. Meanwhile, the president is doing his best to blame the United States for the fiasco, claiming that it had somehow been orchestrated by President Obama .

Venezuelans no longer believe such nonsense. A survey released this month by pollster Alfredo Keller showed that only 1 percent said the United States was to blame for the country’s crisis, while 76 percent blamed Mr. Maduro and the regime founded by Hugo Chávez. Three-quarters said they believed children were dying because of a lack of food and medicine, and 98 percent said they had been unable to find essential products. Only 19 percent said they still supported the regime.

That the Maduro government somehow staggers on is due to its refusal to allow a constitutionally permitted presidential recall referendum ; a divided opposition; a military deeply compromised by corruption, including drug trafficking; and the diversion of international pressure — including from the United States — into feckless and futile attempts to promote negotiations between the government and the opposition. Instead of an election-driven political transition or a people-powered revolution, Venezuela is undergoing a comprehensive breakdown of order unlike anything Latin America has seen in decades. That its hemispheric neighbors witness this implosion without using the means they have to bring meaningful pressure to bear on the government renders the failure all the more profound.