After the bridge collapse Minneapolis on Aug. 1, the Department of Homeland Security announced that there was no evidence of terrorism. Similar declarations followed the July explosion of an 83-year-old steam pipe in Manhattan and an August 2003 power blackout that affected 50 million people and shut down airports across the Northeast. All very alarming, but no terrorism here. Carry on.
This is a curious form of reassurance. Instead of sporadic attacks by a loosely organized enemy, we face a systematic threat well distributed across the nation. The strain on our foundations can cut Americans off from their jobs, their families and...