Was America attacked by Muslims on 9/11?

Much of America's foreign policy since 9/11 has been based on the assumption that it was attacked by Muslims on that day. This assumption was used, most prominently, to justify the wars in Afghanistan and Iraq. It is now widely agreed that the use of 9/11 as a basis for attacking Iraq was illegitimate: none of the hijackers were Iraqis, there was no working relation between Saddam Hussein and Osama bin Laden, and Iraq was not behind the anthrax attacks. But it is still widely believed that the US attack on Afghanistan was justified. For example, the New York Times, while referring to the US attack on Iraq as a "war of choice," calls the battle in Afghanistan a "war of necessity." Time magazine has dubbed it "the right war." And Barack Obama says that one reason to wind down our involvement in Iraq is to have the troops and resources to "go after the people in Afghanistan who actually attacked us on 9/11." . . .

Is it conceivable that this assumption might be false? Insofar as Americans and Canadians would say "No," they would express their belief that this assumption is not merely an "assumption" but is instead based on strong evidence. When actually examined, however, the proffered evidence turns out to be remarkably weak. . . .