Former Dearborn, Michigan, resident Mahmoud Youssef Kourani was a secret Hezbollah agent sent to infiltrate America in February 2001. He stole over the Mexican border into California with a skill set that court records would later describe as “specialized training in radical Shiite fundamentalism, weaponry, spy craft, and counterintelligence,” picked up in Lebanon and Iran. Kourani got caught in 2004 and thrown in federal prison for raising money and recruits for Hezbollah, which pioneered the modern art of suicide truck bombing by blowing up American Marines in Beirut. But the enduring significance of Kourani isn’t that Hezbollah was able to...