By Tricia Bacon, Assistant Professor of Justice, Law & Criminology, American University. Manhattan on Sept. 11, 2001 AP Photo/Daniel Hulshizer Sixteen years ago, on September 11, 2001, al-Qaida conducted the most destructive terrorist attack in history. An unprecedented onslaught from the U.S. followed. One-third of al-Qaida’s leadership was killed or captured in the following year. The…