The bulk of the estimated reductions in health spending come from Medicaid, which will lose more than $1 trillion. Of the 11.8 million people who could lose health insurance, 1.4 million are people without "verified citizenship" or "satisfactory immigration status," the CBO noted.

Senate GOP version of the tax bill would strip 11.8 million people of health insurance over the next decade, CBO estimated.

A report says 20,000 people in South Dakota could become uninsured if the tax bill passes and the Affordable Care Act's enhanced tax credit expires.