Well, it all started with the USA's powerhungry self deciding its cool to start drilling for oil all over the world, and part of that being on holy land (as considered by the afghan people), this eventually led to disputes between the two governments and as such the USA was put onto the Al Qaeda blacklist.
9-11 could have been prevented had the us government decided to drill for oil in other places in the world instead of ripping up part of bumforget texas to get the oil there.
God damn and you wonder why half the world hates the US.