No one in the Iranian government was sad to see U.S. and NATO troops leave Afghanistan. In fact, Tehran would prefer to have the Taliban next-door than often-hostile Western powers. But Shiite-majority Iran has also been a target of attacks in the past from the Sunni Islamist Taliban, and it worries that if Afghanistan descends into chaos, it could negatively affect Iran’s ability to exert influence and trade with its neighbor—or worse, that the volatility could spill over into Iran. Tehran will have to pull off a delicate balancing act if it’s to benefit from the U.S. and NATO withdrawal. […]