I do think that 911 would have happened anyway, because the US needed a "Pearl Harbor" type event to launch them on this global war on terror, which has legitimized their imperial expansion.
Zbigniew Brzezinski wrote in his book The Grand Chessboard:
"It is also a fact that America is too democratic at home to be autocratic abroad. This limits the use of America's power, especially its capacity for military intimidation. Never before has a populist democracy attained international supremacy. But the pursuit of power is not a goal that commands popular passion, except in conditions of a sudden threat or challenge to the public's sense of domestic well-being. The economic self-denial (that is, defense spending) and the human sacrifice (casualties, even among professional soldiers) required in the effort are uncongenial to democratic instincts. Democracy is inimical to imperial mobilization."
and
"In brief, for the United States, Eurasian geostrategy involves the purposeful management of geostrategically dynamic states and the careful handling of geopolitically catalytic states, in keeping with the twin interests of America in the short-term: preservation of its unique global power and in the long-run transformation of it into increasingly institutionalized global cooperation. To put it in a terminology that hearkens back to the more brutal age of ancient empires, the three grand imperatives of imperial geostrategy are to prevent collusion and maintain security dependence among the vassals, to keep tributaries pliant and protected, and to keep the barbarians from coming together."
While Zbig was the National Security Advisor for a Democratic President Jimmy Carter, he was widely considered to be a neo-conservative. His ideas have great influence among the Bushites, and his Council on Foreign Relations and Trilateral Commission along with PNAC, have dictated American foreign policy since Bush Sr. was emperor.
Again from the 9/11 timeline we read:
Former National Security Adviser Zbigniew Brzezinski publishes a book in which he portrays the Eurasian landmass as the key to world power, and Central Asia with its vast oil reserves as the key to domination of Eurasia. He states that for the US to maintain its global primacy, it must prevent any possible adversary from controlling that region. He notes, “The attitude of the American public toward the external projection of American power has been much more ambivalent. The public supported America's engagement in World War II largely because of the shock effect of the Japanese attack on Pearl Harbor.” He predicts that because of popular resistance to US military expansionism, his ambitious Central Asian strategy can not be implemented “except in the circumstance of a truly massive and widely perceived direct external threat.”
So, in the interest of global expansionism, a 911 type event would have had to occur, even if the US had control of Iraq in 1991.