After nearly 20 years, the U.S. has withdrawn its troops from Afghanistan, and the Taliban has regained control over the country. In light of those developments, a panel of foreign-policy experts on Tuesday addressed two separate but related questions: Why did the U.S. military action in Afghanistan fall short, and what comes next for the strife-ridden country? The event occurred as observers are still digesting the rapid collapse of the U.S.-backed national government in Afghanistan, which could not maintain power as the U.S. undertook its military withdrawal. “Even I didn’t…