Working-age adults who live in small towns and rural areas are more likely to be covered by Medicaid than their counterparts in cities, creating a dilemma for Republicans looking to make deep cuts to the health care program. About 72 million people — nearly 1 in 5 people in the United States — are enrolled in Medicaid, which provides health care coverage to low-income and disabled people and is jointly funded by the federal government and the states.