Why Are We Worried About Afghanistan, Exactly?

Sorry for saying this again, but I'm not clear about why Afghanistan is the central front in the war on Islamist terror. Afghanistan did not produce the terrorists who perpetrated the 9/11 attacks, nor did it have a central role in the creation of the ideology of those terrorists (the Soviet defeat in Afghanistan, of course, created feelings of superiority in Islamists, but that's another story). It is an Arab-made ideology, and to a lesser though still important degree, Pakistani-made, ideology that concerns us most. And it is Arab and Pakistani terrorists who are our main concern. Obviously, the U.S. should be in the business of denying safe havens to al-Qaeda terrorists in Afghanistan, but occupying and reforming a country that has proven itself so resistant to occupation and reform, and which isn't the at the root of the ideology we claim we're fighting -- I'm not sure I get it. A more central front is Pakistan; another more central front is Yemen. Cairo, London and Paris are also central fronts. Iran is a central front of a different sort. And yes, Iraq is a central front. But Afghanistan?

And no, I'm not advocating an invasion of Pakistan or Yemen or Cairo or London. But I believe that we should at least get our categories straight. Victory in Afghanistan won't do much to change what is essentially an Arab problem.