NEW YORK, Sept 8 (Reuters) - Two proposed mergers of U.S. health insurers worth tens of billions of dollars would hurt competition in commercial health plans in as many as 17 states, the American Medical Association, the U.S. group that represents physicians, said on Tuesday. Aetna Inc announced plans to buy smaller rival Humana Inc in early July and Anthem Inc agreed to buy Cigna Corp later that month... More