"externally-produced series of events"????
Everyone of the terrorists was living and working and playing right here - and yes looking and acting like "legimate" citizens or "residence" for the most part. And, yes while much of their activity appeared "normal" and non-criminal on the surface, as does all of your activity, it wasn't non-criminal in the broad nature of it. So, yes, hidden among all this "normal" activity of the law-biding citizens of this country are the activities of a foreign army, hidden among us and among all our "normal" activity. And yes, it is the governments job to ferret out this invader and to do so the government must look at all the means by which the "criminal" activity can be discovered lying in among the "normal" activity.
Or, like you, we can ignore them and quit responding when they blow up more things.
What you have to get over is the fact that they are here, they are doing every thing they can to make their criminal activity look like every part of our every day lives, until the day they set to execute their plans. As a consequence, it is only by being able to look at what seems like normal activity to you and I, will the government find the activity of the terrorists.
They were not American citizens.
You want to cure the cold by shooting the dog.