And the tax bill would lead to 1.8 million more people lacking health insurance in California than currently, another 1 million people becoming uninsured in Texas, and more than 800,000 newly uninsured in New York and Florida each, the report said.
Cumulatively, 13 million more people nationally would become uninsured.
The analysis by the left-leaning Center for American Progress also highlighted that the federal Medicare program could be subject to annual funding cuts that would start with $25 billion next year if the Senate tax bill becomes law. The cuts would result from automatic spending reductions triggered by the bill.
"The majority's plan is clear: take away your health care to pay for their tax cuts," said Sam Berger, senior policy adviser at CAP.
The analysis was released two days after Senate GOP leaders added repeal of Obamacare's individual mandate to the their tax bill.
That mandate requires most Americans to have some form of health coverage or pay a tax fine.
Senate Republicans want to repeal the mandate as part of the bill because doing so would save almost $340 billion in federal spending over the next decade — savings which in turn would be used to increase tax cuts to corporations and individuals.
Those savings would come from repeal of the mandate leading to what the Congressional Budget Office has estimated would be 5 million fewer people enrolled in Obamacare individual health plans, and 5 million fewer enrolled in Medicaid, the government-run program for the poor. Another 3 million people who now get coverage through a job are expected to become uninsured as well.