The influential sister of North Korea’s leader warned Tuesday that her country is ready to take “quick, overwhelming action” against the United States and South Korea, a day after the U.S. flew a nuclear-capable B-52 bomber in a demonstration of strength against the North…The U.S.-South Korean training on Monday involving the B-52 bomber over the Korean Peninsula was the latest in a series of drills between the allies in recent months. Their militaries are also preparing to revive their largest field exercises later this month.