ATLANTA — President Barack Obama’s goal of pulling troops out of Afghanistan at the end of next year and the administration’s recent talks with Iran point to a crisis, Sen. David Perdue said Friday on the return from a trip to the Middle East. “This trip reinforces my opinion that we — along with a constitutional crisis and a financial crisis — we do have a global security crisis,” he said. He spoke with reporters by phone from Mendenhall Air Force Base in England moments after his plane touched down from a visit to Israel, Jordan, Kuwait, Afghanistan and Iraq.