State Public Option Act This bill allows residents not already eligible for Medicaid who are not concurrently enrolled in other health insurance coverage to buy into a state Medicaid plan beginning January 1, 2018. The bill makes such buy-in coverage eligible for premium subsidies and reduced cost sharing under the Patient Protection and Affordable Care Act. The Agency for Healthcare Research and Quality shall develop standardized, state-level metrics of access to, and satisfaction with, providers for individuals enrolled in state Medicaid plans. Primary care services furnished under Medicaid by certain providers must be paid at a rate that is not less than the rate under Medicare part B. Beginning in FY2019, the Department of Health and Human Services may award grants to states for the purpose of improving access to services for individuals enrolled in state Medicaid plans. The bill provides the enhanced federal medical assistance percentage to every state that expands Medicaid coverage for individuals who are newly eligible under the Patient Protection and Affordable Care Act, regardless of when such expansion takes place.