As many legislatures around the country have finished their work for the year, fewer than one-fourth of states have taken concrete steps to create health insurance marketplaces, a central feature of the federal law to overhaul the U.S. health-care system. A total of 43 states, meanwhile, have made fresh cuts to Medicaid, even as lingering unemployment and diminishing access to private coverage continue to drive up the number of Americans turning to the public insurance program for the poor. Taken together, these trends highlight the ground-level challenges that health care poses to states.