(Reuters) - The United States carried out air strikes on Saturday against Islamic State fighters near the besieged Shi'ite town of Amerli in northern Iraq and airdropped humanitarian aid to civilians trapped there, the Pentagon said. President Barack Obama authorized the new military action, broadening U.S. operations in Iraq amid an international outcry over the threat to Amerli's mostly ethnic Turkmen population. U.S. aircraft delivered over a hundred bundles of emergency supplies and more aid was dropped from British, French and Australian planes, officials said, signaling headway in Obama’s efforts to draw allies into the fight against Islamic State. Iraqi...