The half of American states resisting the federal expansion of Medicaid under the Affordable Care Act will forgo $555 million in funding for community health centers providing medical care for the uninsured, while denying Obamacare coverage to one-million qualifying Americans.

Within those 25 states are 518 of the country’s 1,128 community health centers, or “clinics,” which serve 5 million Americans who lack health insurance coverage, according to a new report from the Geiger Gibson/RCHN Community Health Foundation Collaborative at the George Washington School of Public Health and Health Services.

"Our analysis shows that if you are poor and live in one of the 25 opt-out states, you are likely to have been left out when it comes to health reform," lead researcher Peter Shin, director of the Geiger Gibson Program in Community Health Policy, told reporters. "Community health centers in the opt-out states will be faced with waiting rooms filled with uninsured patients, many with serious and costly health problems."

America’s network of community health centers provides comprehensive medical care to the uninsured in 8,000 underserved urban and rural communities, from New York City’s Harlem neighborhood to St. Charles, La. Although poor, these patients don’t qualify for traditional Medicaid benefits and often cannot even afford to pay for health insurance coverage at reduced rates, even lower rates to be offered on the coming health insurance exchange markets in states participating in Obamacare.

To date, 72 percent of the one-million uninsured community health center beneficiaries live in Southern states, many of which compose the 25-state block declining to expand Medicaid. Shin and his colleagues analyzed data from a 2009 survey of clinic patients as well as a 2011 survey used as a standard report by community health centers to the U.S. Health Resources and Services Administration. In their findings, the community health centers will forgo hundreds of millions of dollars in federal money while still serving those patients, depending solely on state money.

Uninsured patients in those states will continue to face barriers to receiving medical care, including long waiting periods and long drives. Moreover, clinics in those states will be unable to follow other states—such as Vermont, even before Obamacare—in expanding basic medical care to providing mental health and dental care, too.

"Health centers in the opt-out states will face an ongoing struggle to meet the need for care in medically underserved communities as a result of the potential loss of hundreds of millions of dollars in revenues in 2014 alone," Sara Rosenbaum, report co-author, said.

However, the 582 community health centers located in the other half of America—including many so-called “blue states”—will receive increased revenue next year as 2.8 million of their patients gain healthcare coverage, translating into a potential windfall of more than $2 billion. With more funding, these clinics will hire additional staff members while providing expanded service to clients. Ohio’s recent entry into the Medicaid expansion netted the state’s 33 community health center $29 million in federal funding, with 63,000 residents expected to gain coverage through lowered or subsidized plans offered through Obamacare.

Feygele Jacobs, president and CEO of the RCHN Community Health Foundation, told reporters the “opt-out” states would continue to fall behind others in quality of medical care for poor Americans.

“Community health centers represent the backbone of the nation's safety net, providing high quality care to more than 20 million Americans who live in underserved neighborhoods,” Jacobs said. "Without the Medicaid expansion, CHCs in opt-out states will fall behind and will have trouble providing the kind of care that keeps people and communities healthy."