"William Braniff, the executive director of the National Consortium for the Study of Terrorism and Responses to Terrorism at the University of Maryland, said the outsize fear of jihadist violence reflected memories of Sept. 11, the daunting scale of sectarian conflict overseas and wariness of a strain of Islam that seems alien to many Americans. “We understand white supremacists,” he said. “We don’t really feel like we understand Al Qaeda, which seems too complex and foreign to grasp.”"