To prevent another disaster, we must understand what happened. We have named it asymmetric warfare. We should understand why America was attacked, for it relates to our own history. The colonies fought the first part of the revolutionary war that way. The little guy can not fight the same way as the big guy.
When we grew more powerful, we decided that nobody ELSE would get to exercise any power in the Western hemisphere with the Monroe Doctrine, resenting Europe's meddling in South American affairs. That did not mean we would not medle in their affairs. We supported the 9/11/73 coup d'état against the democratically elected Salvador Allende, ending the Chilean democracy started in 1932, and putting Augusto Pinochet in total power and establish an anti-communist junta. Henry Kissinger said "I don't see why we need to stand by and watch a country go communist due to the irresponsibility of its own people. The issues are much too important for the Chilean voters to be left to decide for themselves." It was only later that we decided we did not like Pinochet, just as we decided we did not like Castro after we helped him oust Batista, who we had helped to power.
The developed Western nations have been meddling in middle eastern affairs, obvious in the creation of the map of Iraq, with Kurds and Shiite and Sunni, all of whom want their own nation. The U.S. replacing the elected leader of Iran with the Shah, taking Ossama bin Laden off the terrorist list to support him against Russia, supporting Saddam with arms against Iran, and continual manipulating the people of the middle east did not endear us to the people.
Not surprisingly, some resent it, not the least Ossama bin Laden, our previous tool. He is doing to us what we used him to do to the USSR: bankrupt us, for he can not win with arms. He can scare us into bankruptcy, ending our ability to manipulate middle eastern politics and limit fundamentalist Muslims. Money that was earmarked to repair the levies in New Orleans was reallocated to Homeland Security (oops) and the War on Terrorism, thereby following Ossama's script. We have lost the Fourth, Fifth, and Sixth Amendments to the administration's war on Terrorism, again having exactly opposite the effect Americans intended. Bush supported Israel in it's war, in spite of its' use of 100,000 cluster bombs on southern Lebanon after a cease fire was decided, convincing many that America is waging war against Muslims.
We can do better. Isolationism does not work, and we are learning (I hope) that manipulating others does not work. The world keeps remembering Machiavellian support of the Shah of Iran, Sadat, Mubarak, Marcos, Mobutu, Suharto, Pinochet, Franco, Papa Doc, Baby Doc, and other despots. With NATO and the U.N., we have intervened, and as a result, Eastern Europe is calmer.
Ossama's original intent of 100,000 lives with the Twin Towers was a miserable failure with 2752 lives, but it was our response that has cost more American lives, and threatens more as well as our future.