308wood,
I think the title of your post is a little misleading. It seems to me, that you are talking about U.S. foreign policy in general – rather than the specific war on terrorism.
My remarks concern your the title of your post. There are two types of terrorism:
Individuals – be they national (McVeigh, Unibomber or the Anthrax wacko) or foreign nationals. These people you cannot stop – no matter what! Their aim is simple: to cause injury as a means of eliciting revenge in response to perceived injustice of some kind.
Terrorist Groups: Bader Meinhof, Red Brigade, R.A.F., Al Qeada. The aim here is far more grandiose: To overthrow the status quo; to cause governments to institute measures that incite the citizenry – I.D. cards, stupid airline searches, restrictive firearms regulations, stop and search procedures without warrants, phone and computer tapping ect.
These groups can be prevented from orchestrated, organized and devastating attacks (9/11) by doing what the U.S. is currently doing, i.e., attacking their ability to organize and finance such orchestrated attacks.
The reason that the Afghan affair was a retalliatory measure that cost billions is because the U.S. (and others) did not spend the millions to gather the intelligence that might have prevented 9/11 in the first place. In other words it was a reactive measure (like the decades of similarly flawed Israeli policy of retalliation), rather than a proactive effort.
You cannot ever erradicate terrorism for it is limited only to the imagination of a single fanatic – and I, together with many members here, know how easy that is to bring about.