Some current and former U.S. officials warn the event would be a distraction when the U.S. faces threats from Iran-sponsored groups driven by the war. WASHINGTON, March 31 (Reuters) - The Trump administration is organizing an international summit focused on countering the left-wing movement antifa and other groups, three sources familiar with the matter said, an effort that highlights the shift in the U.S. government’s counterterrorism priorities over the past year. The conference, tentatively