Sigh...... Let me explain it to you in terms you may understand. Do you worry about getting killed in an airplane accident? Do you worry about choking to death on your food? Do you worry about being poisoned to death? The odds of dying in a terrorist attack in the US at least are less than the above.
Sigh... let me explain it in terms that you may understand, but I am not sure you will understand the nuance of the issue. I gave you a really good example of a situation where the odds do not really matter, it is about what we have learned. We learned that lightening is very dangerous,and that we should stay away.
Islamic terrorism is in the same category. Now part of that is fueled by a bit of paranoia. But a big part of that is a result of the constant propaganda and threats from Islamic Terrorists. We did not create a fear of lightening, and we did not manufacture the fear of Islamic terrorism, but both have been ingrained in the psyche of most people around the world. That is not 100% our fault.
I agree that it is not worth getting "worked up" about, but it is also silly not to take some precautions. As I write this, I ask myself the question if I was given a free trip to London, would I take it? The answer is a solid maybe. Will I stay away from any Canada Day celebrations? Normally, I would say definitely not, but my answer is maybe.
Finally, the reality is that we in Canada are overdue for an attack, it is only a matter of time.