OUR son lives next to a Turkish mosque on Kingsland Road in Hackney, where some of London’s worst mob violence has occurred. When looters rampaged through Hackney last weekend, there were few police officers to stop them and residents had to chase them off with butcher knives, truncheons and baseball bats. Vigilante action succeeded where normal policing failed.

Kingsland Road resembles the bustling, ethnically mixed streets of Brooklyn. During the day, it is a home of sorts for unemployed young men with nothing to do; Britain’s youth unemployment rate is currently over 20 percent. During the economic boom a decade ago, though, nearly as many were out of work, and they did not all turn to crime.

To counter the risk that they might, there were storefront drop-in centers for young people in the neighborhood; these places are now shutting down, as are other community services, like health centers for the elderly and libraries. Local police forces have also been shrinking.

All are victims of what people in Britain call “the cuts” — the government’s defunding of civil-society institutions in order to balance the nation’s books. Before the riots, the government had planned to cut 16,200 police officers across the country. In London, austerity means that there will be about 19 percent less to spend next year on government programs, and the burden will fall particularly on the poor.

The rioters in London appear to be young men of varying races — despite reports of a monolithic mob of alienated “black youth.” But there is a racial dimension to this drama. The wave of riots began with protests against the police killing of a young black man, Mark Duggan. While initially peaceful, the demonstrations soon descended into violence. When the unrest spread to Manchester on Tuesday, many of the rioters there were apparently white.

An old-fashioned Marxist might imagine that the broken windows and burning houses expressed a raging political reaction to government spending cuts — but this time that explanation would be too facile.

The last time Britain saw widespread rioting, in the 1980s, street violence came after a long and failed political struggle against the Conservative government of Margaret Thatcher, which suppressed trade unions and decimated social services. Today, the rioters seem motivated by a more diffuse anger, behaving like crazed shoppers on a spree; while some of the shops looted are big chains, many more are small local businesses run by people who are themselves struggling through Britain’s economic slump.

There has been a change in national temperament that has affected decent citizens as well as criminals. The country’s mood has turned sour. Indeed, the flip side of Britons’ famed politeness is the sort of hooliganism that appears at soccer matches and in town centers on weekend nights — an unfocused hostility that is usually fueled by vast quantities of alcohol. Fears of anarchic urban mobs date from Shakespeare’s time, and Prime Minister David Cameron has summoned these old fears, describing the present conflagration as “senseless.”

Mr. Cameron was good at selling people on the idea of cutting costs, but he has failed to make the case for what and how to cut: efforts to increase university fees, to overhaul the National Health Service, to reduce the military and the police, even to sell off the nation’s forests, have all backfired, with the government hedging or simply abandoning its plans.

In attempting to carry out reform, the government appears incompetent; it has lost legitimacy. This has prompted some people living on Kingsland Road to become vigilantes. “We have to do things for ourselves,” a 16-year-old in Hackney told The Guardian, convinced that the authorities did not care about, or know how to protect, communities like his.

A street of shuttered shops, locked playgrounds and closed clinics, a street patrolled by citizens armed with knives and bats, is not a place to build a life.

Americans ought to ponder this aspect of Britain’s trauma. After all, London is one of the world’s wealthiest cities, but large sections of it are impoverished. New York is not so different.

The American right today is obsessed with cutting government spending. In many ways, Mr. Cameron’s austerity program is the Tea Party’s dream come true. But Britain is now grappling with the consequences of those cuts, which have led to the neglect and exclusion of many vulnerable, disaffected young people who are acting out violently and irresponsibly — driven by rage rather than an explicit political agenda.

America is in many ways different from Britain, but the two countries today are alike in their extremes of inequality, and in the desire of many politicians to solve economic and social ills by reducing the power of the state.

Britain’s current crisis should cause us to reflect on the fact that a smaller government can actually increase communal fear and diminish our quality of life. Is that a fate America wishes upon itself?