Image caption The beginnings? Historian Rick Perlstein says union protests in Wisconsin show the birth of a movement

New York City Mayor Michael Bloomberg has suggested the unrest that rocked the streets of Cairo and Madrid this year could spread to the US. Is he right?

It was a long, hot spring and summer on the streets of Greece, England and Madrid, as protesters and rioters vented their fury at high unemployment, painful austerity measures and following a fatal police shooting in London.

The US, meanwhile, has been virtually free of rioting and even of widespread peaceful political protest.

This is despite some of the highest unemployment in decades, growing income inequality, dissatisfaction with the nation's direction, frustration with its dysfunctional government and the threat of drastic cuts to social programmes.

On Friday, Mr Bloomberg raised the spectre of social unrest amid high unemployment among young Americans.

Upheaval in Europe and North Africa England: Riots erupted last month, sparked by the police shooting of a black man in north London. More than 1,700 people arrested

Riots erupted last month, sparked by the police shooting of a black man in north London. More than 1,700 people arrested Greece: Protesters clashed with police in June as MPs voted in an austerity package

Protesters clashed with police in June as MPs voted in an austerity package Madrid: Since May, demonstrators have taken to the streets over government's handling of the economy

Since May, demonstrators have taken to the streets over government's handling of the economy Arab Spring: Popular revolts have toppled regimes in Tunisia, Egypt and Libya

"You have a lot of kids graduating college, can't find jobs," he said on a radio show.

"That's what happened in Cairo. That's what happened in Madrid. You don't want those kind of riots here. The damage to a generation that can't find jobs will go on for many many years."

In the past century, the US has experienced its share of political tumult and unrest, from the destitute "Bonus Army" veterans of World War I who clashed with federal troops in Washington in 1932, to the urban race riots in the 1960s and the Rodney King riots in 1992.

And in interviews with the BBC, analysts, writers and historians feared the US was ripe for some sort of social upheaval, but said a lack of social organisation and a sense of despair had prevented social movements from coalescing.

Image caption The brutal beating of Rodney King by white Los Angeles policemen touched off rioting in 1992

"It's amazing to me that Americans are so slow to rise collectively... not only against unemployment but against the quite identifiable forces that are responsible for it," said sociologist Prof Todd Gitlin of the Columbia University journalism school.

"I'm not predicting that such a thing will happen, but it would not in the slightest surprise me if there were some burst of street expression, some street rage."

'Quiet riots'

Gary Bailey, a professor of social work practice at the Simmons College School of Social Work in Boston said "draconian" austerity cuts contemplated in the US Congress could eventually spark unrest if young Americans felt their future was being taken from them through cuts to education and jobs programmes.

"We are inevitably at risk," he said. "We're not immune to what's happening in the world. The bigger the city and the larger the youth population, the greater the risk.

Social turmoil in the US Bonus Army march 1932: As many as 65,000 impoverished WWI veterans and their families clash with troops after gathering in Washington to demand cash payment of pensions

As many as 65,000 impoverished WWI veterans and their families clash with troops after gathering in Washington to demand cash payment of pensions Watts Riot 1965: Anger over a white policeman's arrest of a young black man for drink-driving touched off six days of riots in LA. 34 people killed, more than 1,000 injured

Anger over a white policeman's arrest of a young black man for drink-driving touched off six days of riots in LA. 34 people killed, more than 1,000 injured Kent State shootings 1970: After National Guard troops fire at anti-war demonstrators, killing four students at Kent State University in Ohio, a national student strike shuts schools and universities round the US

After National Guard troops fire at anti-war demonstrators, killing four students at Kent State University in Ohio, a national student strike shuts schools and universities round the US Rodney King riots 1991: LA again erupted after four white police officers videotaped beating black motorist Rodney King were cleared of assault charges. 55 people killed and 2,000 injured

"What Mayor Bloomberg was warning of was that this disenfranchisement, for lack of a better word, leads to despair and unrest.

"He makes the point of the Arab spring, which came out of what happens when you have disenfranchised youth.

"When they look at power being vested in a very few, and very often in whom they cannot see themselves reflected, societies are very much at risk."

But Peter Dreier, professor of politics and director of the urban and environmental policy programme at Occidental College in Los Angeles, said Americans do not have the "psychology of rioting", and said Americans who bear the brunt of the economic downturn are "demoralised" and discouraged from taking collective action.

"People are angry, and right now they're taking their anger out on themselves - the quiet riots of suicide and depression," he said.

"It took about three years into the Depression before people overcame this sense of blaming themselves about their plight, before they got angry at the banks and the business community and local mayors, before they externalised their anger and made it a political issue rather than a personal one."

'Anomie'

Even as unemployment hovers at 9.1%, median household income decreases, and more people are impoverished than at any time in the last 52 years, Prof Gitlin said life remains tolerable for most Americans.

Image caption In 1967, riots erupted in Newark, New Jersey after a black taxi driver was beaten by police

That may explain why Americans have not taken to the streets en masse, he said.

"It's one thing to know in the sense of 'I read this in the newspaper' that inequality is at its peak, that upward mobility barely exists, that the public sector is being stripped," he said. "It's not that daily life is unliveable as a result."

Rick Perlstein, a historian and author of Nixonland: The Rise of a President and the Fracturing of America, said Americans suffer from a "profound sense of learned helplessness".

"The fact is the American population - even if they rose to that level of anger - they don't feel that they have anybody to address that anger to, any responsive bodies," he said. "That's a function of the breakdown in trust in government. It's a function of anomie and frustration."

Image caption In 1965, the drink-driving arrest of a black motorist sparked days of riots in Los Angeles

But Mr Perlstein pointed to union protests in Wisconsin, Ohio and Indiana this year against anti-union measures in state legislatures there, to a massive strike by workers at telecommunications firm Verizon, and constituent meetings this summer at which voters angrily confronted congressmen about feared cuts to social programmes.

"We are seeing a widespread social movement," he said. "The fact that there isn't a media narrative about interesting things happening says more about the media."