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 Republicans have unveiled a sweeping plan to overhaul the Medicaid program, with changes policy analysts warn could lead to even greater coverage losses and pain for hospital systems than the aggressive proposal passed by the House of Representatives last month.