Answer: You can't keep milking the cow for ten years.
Black Tuesday was a tragedy. Yes, it was a crime perpetrated by people who deliberately put themselves beyond the pale of civilized behavior as we understand it. While the radical's motives were unjustifiable to us, their motives were perfectly justifiable to them. They shall not be revisited here, in the interest of brevity.
However, what happened after 9/11/01 was not a crime. It was worse. It was a mistake.
As the dust and debris settled, the rest of the world stood with us. Even Iran and the PLO, for Cthulhu's sake, supported us. NATO activated the collective security clause of the North Atlantic Treaty out of sympathy for our cause. As the injured party (and there is no doubt we were injured on that day) we had the moral high ground.
We squandered that moral position, so badly that now not even the British trust our motives unreservedly any longer - so much for the "special relationship." We beat down the Taliban in Afghanistan, and had al Qaeda pinned down in the Tora Bora region. Then, we took the eye off the prize and went haring off to attack Iraq.
We had no business attacking Iraq. Iraq had nothing to do with 9/11, and none of the 19 hijackers were Iraqis (fourteen were Saudis, but we didn't invade Saudi Arabia for it). Saddam and Osama mutually loathed each other - Saddam considered Osama to be a religious extremist troublemaker, while Osama considered Saddam to be a socialist secularist apostate. I watched and listened to Colin Powell prostituting himself at the UN Security Council, and I was unconvinced that we had any casus belli in Iraq.
Shortly after we invaded Iraq, one of my coworkers (who gets all his news from Fox and Townhall.com) told me that we were at war and that I should shut up and follow the President. I pointed out that that's a pretty slavish and servile thing to do in a democracy, war or not - and besides, I asked, if we were truly at war, why weren't taxes up? Why weren't we conscripting? In response, he called me a liberal (which is wrong on several fronts).
We gave up our moral position, and frittered away the respect that we once enjoyed. And anyone will tell you that respect, once lost, takes a hell of a long time to gain back.
We borrowed, hand over fist, with ruinous consequences for our economy. Osama said himself that he didn't NEED to defeat the USA militarily - all he had to do was bleed us white economically. I will state, here and now, that he won that fight, with a lot of help from a bunch of greedy bastards in this country and in Europe.
We have stretched our military forces - the finest body of fighting men and women on Earth - to the breaking point and even beyond in some cases.
We have vomited up some of our most cherished ideals, including the idea that we can be secure in our homes, property, persons, etc. from government intrusion. We have willfully violated international treaties, which under our Constitution have the force and effect of Federal law.
And so matters stand, ten years on.
Ten years ago, I quoted Aeschylus: "Cry sorrow, sorrow - yet let Good prevail!"
Good has not prevailed.