There are reasons why people become islamic terrorists. The reasons differ from the region, though. The reasons for muslims in Europe to become terrorists are different from those in the developing world. A key factor in the developing countries seems to be demographic, i.e. the youth bulge of the islamic world and the lack of positions for the mass of young people in their economically underdeveloped countries. See
http://en.wikipedia.org/wiki/Youth_Bulge#Youth_bulge
In Europe, it seems to be more a problem of weakness of western civilisation and failed integration, which roots in western cultural exhaustion and identity crisis. (I don't really have time to get into this right now, maybe I will write more later)
But back to the reasons most people think of.. So, what are the jihadists fighting for? Why do they fight the West (and "westernized", i.e. democratic and/or secular muslim countries)?
9/11 didn't happen because of US foreign policy. America was attacked for what it
is, not what it did. Secularism, women's rights, freedom of speech, religious freedom, gay rights, etc. are the reasons why jihadists fight it.
They want the caliphate back. They want sharia law in every country, religious and gender apartheid, and in the end islamic rule over the world. It's a religious supremacy movement, it doesn't need real world events to fuel it's ideology.
It doesn't matter whether the US goes into Iraq or chooses to be isolationist. As long as America, Europe or any place else is not part of the "House of Islam" and doesn't bow down to jihadism and islamic rule, it's the enemy for the jihadists.
So, how to deal with those reasons? Abolish democracy and introduce sharia law to the West? Convert to Islam? Accept dhimmitude if you want to stay christian or jew? Rather not.