Millions of Americans in conservative-leaning states could remain without health insurance after the Supreme Court’s decision last week to strike down part of President Obama’s health care law.

While upholding most of the Affordable Care Act, the Court, in a 7-2 ruling, struck down a requirement in the law that states put virtually all of their low-income people in Medicaid. Under the original law, states would have lost all of their Medicaid funding if they didn’t offer insurance to anyone who makes less than 138 percent of the federal poverty level, which is about $15,000 for an individual and $30,000 for a family of four.

After the court’s ruling, states can refuse additional Medicaid money that is tied to that requirement, but they can keep the funds they currently get from the federal government.

Republicans have long opposed expanding Medicaid, a government-operated insurance program, casting it as another step to a European-style health system.

And this could have a dramatic effect on the reduction in the number of uninsured under “Obamacare.” Many of the states with the highest percentage of people who are uninsured, such as Mississippi, Texas, Florida and Louisiana, have conservative, anti-Obama governors who for ideological and political reasons may be opposed to agreeing to any expansion of Medicaid.

And some of them are balking at the cost. Under the law, the states would have to pay for about 10 percent of the costs of expanding Medicaid, which will add to up to tens of millions of dollars. (To be sure, the federal government would pay 90 percent of the new Medicaid costs, and states, local governments and hospitals currently spend millions paying for the care of people who come without insurance)

More than a quarter of the people in Texas don’t have health insurance, the highest rate in the country, and the Urban Institute estimates more than two million people there could get insurance under the Medicaid provision. But Gov. Rick Perry is a strong opponent of the health care law, as is Florida’s Rick Scott, where more than one million could get coverage.

Overall,17 million Americans were expected to benefit from the Medicaid expansion, but the liberal Think Progress has estimated that more than half of them live in states that have not yet said if they will accept the new funding requirements.

These decisions are particularly important for minorities, who disproportionately lack health insurance. In many of the states which are considering not accepting the Medicaid funds, such as Mississippi and Alabama, more than a fifth of the residents are black, while Texas is about 38 percent Hispanic.

Follow Perry Bacon Jr. on Twitter at @perrybaconjr