War on Terrorism from the viewpoint of an American

I know that there truly are terrorists, and that every country does have to have a certain amount of security when dealing with it.

However, growing up the only real act of terrorism I had heard of before 9/11 was the Oklahoma City Bombing, which wasn't even from a terror group like Al-Queda, but by a home grown terrorist. If the war on terrorism is so all encompassing and so important, why did our governments decide that now should be the time to act(via 9/11/01)?

If terrorism has been such a threat to our nation's growth, then why let it run around free for a decade or two or three without any sort of response?

I ask why is it so important now? But I know military strategy, when you see an opening that will benefit you, you take it. If the consequences become questioned, you create a scapegoat or rationalize with those seeking answers.

Not so much importance on this thread. I've just thought about this since 9/11 (even being 11 at the time it seemed questionable, especially declaring war 3 days later with the approval of congress) and with the recent fiasco about Osama Bin Laden, I felt I would bring these points up.