Car accidents and terrorism are apples and oranges. I find this argument to be repulsively dismissive of life. It sounds like the, "That stuff only happens to other people, not me" mindset. Until it happens to you or someone close to you. When people die in a car crash, it's an accident. It's random. Shit happens, but no one was [i]intentionally[/i] trying to mow you down in their car. That's the whole difference. Intent is the big deal, because there's a human intelligence creating and driving it, not random circumstance, and that intent is to cause and increase the pain, suffering, and death as much as possible. (And if a car accident killed 20, 100, or 2,000 people in a single event, I think it'd get a LOT of attention). Admit it or not, but one of the reasons so few people have died via terrorism is probably because there's a ridiculously lopsided massive effort to fight it.(though the TSA is a bit of a joke).
If the system simply said, "Big deal, more people die in car accidents" and did nothing, there'd be more terrorist attacks and deaths, because it's not for lack of trying on the part of ISIS and AQ, who clearly want to, who have have the resources to. And while the feds can't catch everyone (Boston bomber) that doesn't mean they don't thwart others.
Just to clarify, I'm not justifying the intrusion on the Constitution, just addressing the car deaths analogy.