WASHINGTON — When terrorists attacked New York and Washington in 2001, the Middle East was firmly in control of authoritarian leaders. Some of them were staunch allies of the United States who tolerated the growing threat from Osama bin Laden.

A decade later, bin Laden is dead, al-Qaida has been set back, and the autocrats in Egypt, Iraq, Libya, Tunisia, Afghanistan and Yemen have been swept from power by their own people — a series of sometimes deadly protests and battles now known as the Arab Spring.

Although analysts are deeply divided about whether U.S. policy brought about this remarkable transformation, they say that the U.S. is safer today than when the twin towers of the World Trade Center collapsed and nearly 3,000 Americans died at the hands of terrorists.

“In terms of al-Qaida, yes, we are a lot better off today,” said Steven Hadley, who served as President George W. Bush’s national security advisor. “Why? The killing of UBL (bin Laden) is important. He was a Messianic figure, a source for inspiration and the glue that held al-Qaida together.”

“Second, the Arab world and the Muslim world figured out finally that in the name of jihad against the infidels, al-Qaida was overwhelmingly killing Muslims, and it resulted in a dramatic decline of support for al-Qaida and UBL,” said Hadley. “And the coming of freedom and democracy to the Middle East is a repudiation of al-Qaida.”

Retired U.S. Army Colonel Pete Mansoor, a professor of military history at The Ohio State University and a former aide to General David Petraeus in Iraq, said “we can’t take credit for the Arab Spring. It’s pretty clear there was going to be an explosion because these authoritarian regimes couldn’t meet the needs of their growing populations.”

But Mansoor acknowledged that the September 11 attacks, combined with “the U.S. intervention in the region, acted as a catalyst.’’ And he added that he doubts “we would have seen the Arab Spring had we failed in Iraq in 2006. Had Iraq come apart in a civil war, you would have seen a retrenchment of power by the authoritarian regimes.”

Others suggest that the sweeping upheaval in the Middle East that culminated last month with the fall of Libyan leader Muammar Gaddafi was inevitable, and that the U.S. push for democratic change — first by President George W. Bush in 2003 and later by President Barack Obama in a speech last May — played only a minor role.

They argue that Bush’s decision to attack Iraq in 2003 and depose Saddam Hussein actually hampered American efforts to promote democracy in the Middle East. They point out that the successful U.S. invasion was followed by years of messy sectarian violence that required Bush in 2007 to dispatch thousands of troops to Iraq to quell the uprising.

“One of the striking things about the Arab Spring is how little it has to do with us,” said Lawrence Korb, a national security analyst with the left-leaning Center for American Progress in Washington. “If anything, we may have set it back by us going into Iraq under false pretensions.”

For decades, American presidents from both parties backed a series of autocrats in the Middle East and Near East, preferring easy access to oil and political stability over taking a risk with democratic alternatives. The fall of the Shah of Iran in 1979, for example, did not lead to a democracy, but instead to an Islamic Republic that is a sworn foe of the United States.

But in the aftermath of the September 11 attacks, Bush articulated a new U.S. strategy that would promote democracy, saying that “as long as the Middle East remains a place where freedom does not flourish, it will remain a place of stagnation, resentment and violence ready for export.’’

Bush argued that 60 years “of Western nations excusing and accommodating the lack of freedom in the Middle East did nothing to make us safe — because in the long run, stability cannot be purchased at the expense of liberty.’’

When Obama took office in 2009, he showed little enthusiasm for Bush’s approach, giving only tepid support in 2009 to Iranians protesting the apparently fraudulent outcome of that country’s presidential election. But Obama also sent thousands of American troops to stabilize Afghanistan and helped orchestrate NATO efforts this year to aid Libyan rebels oust Gaddafi.

In a speech in Washington last May, Obama edged closer to Bush’s 2003 speech, saying that the U.S. “welcomes changes that advances self-determination and opportunity” in the Middle East. He declared that “after decades of accepting the world as it is in the region, we have a chance to pursue the world as it should be.”

The result — whether by design or fortune — has been stunning. One by one, the entrenched autocrats have fallen: Gaddafi, Hosni Mubarak in Egypt, Saddam Hussein in Iraq, Zine El Abidine Ben Ali in Tunisia, and Mullah Mohammed Omar of Afghanistan.

“Without question, President Obama has distanced himself from (Bush’s) policies,” said Clifford D. May, president of the Foundation for the Defense of Democracies and a former foreign correspondent for the New York Times. “On the other hand, he has been an agent of regime change in Libya, he has doubled down in Afghanistan and I think it would be unfair to say he squandered American and Iraqi victories in Iraq.”

Hadley, who grew up in the Cleveland suburbs, acknowledged that “it’s very hard to know” whether U.S. policy prompted these sweeping changes. “The Arab Spring is being brought to you by the courageous people of the Middle East.”

But he argued that Bush’s change in strategy has been “in some sense vindicated. ... There is no going back. The Mubaraks and Gaddafis and Ben Alis are not coming back. That era is gone. The Middle East isn’t going back and we should do all we can to help these folks succeed in what they clearly want to do — which is to establish free and democratic societies.”

“U.S. policy played a role, but it’s too early to congratulate ourselves on the changes that are taking place,” said May. “We don’t know what Libya, Syria, Egypt or even Tunisia will like a year from now or 10 years from now. Historically, that’s a blink of an eye.”