BAGHDAD—A U.S. airstrike in Syria targeted facilities belonging to a powerful Iranian-backed Iraqi armed group, killing one of their militiamen and wounding a number of others, an Iraqi militia official said Friday. The Pentagon said the strikes were retaliation for a rocket attack in Iraq earlier this month that killed one civilian contractor and wounded a U.S. service member and other coalition troops. The Iraqi militia official told The Associated Press that the strikes against the Kataeb Hezbollah, or Hezbollah Brigades, hit an area along the border between the Syrian site of Boukamal facing Qaim on the Iraqi side. He spoke on condition of anonymity because he was not authorized to speak of the attack. Syria war monitoring groups said the strikes hit trucks moving weapons to a base for Iranian-backed militias in Boukamal. “I’m confident in the target that we went after, we know what we hit,” Defense Secretary …