Beirut: With Iran-backed Hezbollah on the defensive after a series of heavy Israeli blows, the United States and Iran are locked in a showdown over Lebanon’s future, analysts said. Hezbollah, the most powerful regional force backed by Iran, which arms and finances it, has long held sway in Lebanon. But the group’s influence is now in question after Israel’s assassination of its leader, Hassan Nasrallah, in a significant setback.