We didn’t know then what we know today. Some, including many of my friends, warned of the dangers of American hubris. I did not heed them in 2003.

But the greater hubris is to think that what America does or doesn’t do is all that matters. The blame for the catastrophe of post-2003 Iraq must be placed on the new Iraqi political elite. The Shiite political class, put in power by the United States, preached a politics of victimhood and leveraged the state to enrich itself. These leaders falsely identified all Sunni Iraqis with Baathists, forgetting how heavily all Iraqis, including some Shiites, were implicated in the criminality of Mr. Hussein’s regime.

Although I always feared, and warned in 1993, that the emergence of sectarian strife was a risk after Mr. Hussein’s fall, my greatest misjudgment was in hoping that Iraq’s new leaders would act for the collective Iraqi good.

For all its bungling, the Bush administration’s invasion of Iraq exposed a fundamental truth of modern Arab politics. Washington’s longstanding support for autocracy and dictatorship in the Middle East, a core principle of American foreign policy for decades, had helped stoke a deep-seated political malaise in the region that produced both Saddam Hussein and Al Qaeda. By 2003, American support for Arab autocrats was no longer politically sustainable.

The system of beliefs Mr. Hussein represented had ossified and lost the ability to inspire anyone long before 2003. And yet he was still there, in power, the great survivor of so many terrible wars and revolutions. Before the American invasion, it was impossible for Iraqis to see beyond him.

There was hardly any war to speak of in 2003. Mr. Hussein’s whole terrible edifice just came crashing down under its own weight. The army dismantled itself, before L. Paul Bremer, the American proconsul, even issued his infamous and unnecessary order to purge Baath Party members from the military.

Toppling Mr. Hussein put the system of which he was such an integral part under newfound scrutiny. If the 1991 war was about the restoration of the Arab state system, the 2003 war called into question that system’s very legitimacy. That’s why support from Arab monarchies was not forthcoming in 2003, when a new, more equitable order was on the agenda in Iraq.