There are huge outcries in the U.S. about things like surveillance cameras, tracking phone calls, national IDs, closing of borders, and many other things that would be required to try to get a reasonable level of security if you dealt with terrorism only at the final endpoint.

The World Trade Center was bombed in February of 1993, an attack planned as early as 1991. The individual perpetrators were, almost to a man, captured, prosecuted, and punished.

Oddly, this successful police action and prosecution did not end Islamic terrorism against the U.S., and an entirely different set of actors finished the destruction of the World Trade Center less than ten years later, at a time when there were no "imperialists" in Iraq, or even in Afghanistan.

The belief that this is not a war, but a simple series of criminal acts to be dealt with as they come, is probably the major gulf between your side and mine in the perception of this situation.

No matter what our side believes, the other side believes it to be a war of civilizations. Bin Laden's 1996 declaration of war can be read here. I highly suggest you actually read it, and start to get an idea of exactly how many different excuses these people have for killing us.