BOWLING GREEN, KY.—The little red wagon was strewn upside down on a heap of rubble—a pile of boards and bricks, a mangled blue bicycle, a baby doll. Behind it, there was little more than a hole in the ground where a house had stood. Across the street, the tidy homes on this cul-de-sac were reduced to mounds of lumber. Clothes hung from the branches of snapped trees. The walls of one house were gone, and the only thing left standing inside was a white Christmas tree. When a tornado touched down in Bowling Green, Kentucky, in the middle of the night, its violence was centered on this friendly subdivision, where everyone waved at one another and giggling children spent afternoons tooling around on bicycles on the sidewalks. Fourteen people died in a few blocks, 11 of them on a single street, Moss Creek Avenue. Entire families were lost, among them …