The emergency room at Northwestern Memorial Hospital was packed with flu patients when Caleb Stevens hobbled through the doors on crutches one evening in January, his leg pulsing with pain from a week-old gunshot wound. The clerk at the intake desk was unfazed when Stevens said he had been wounded in Syria. She took his passport and told him to join the rest of the people in the waiting room. So he sat with his mom for 20 minutes, his right leg wrapped in a cast, a splint and bloody bandages. He was still wearing a red-and-white Christmas sock someone...