The Trump administration has also withheld funds from insurers that have resulted in higher premiums, reduced the open enrollment period for ACA plans and significantly pared back marketing of the plans.

While most of the Trump administration changes did not impact the cost of plans for the majority of enrollees, whose premiums are based on their income, they drove up the price paid by higher-income customers who did not qualify for subsidies.

There is also speculation that legal immigrants have avoided enrolling in coverage for fear that receiving any type of government subsidy would make it harder for them to gain citizenship. The Trump administration has proposed a "public charge" rule that would make it harder for those who have received government benefits to become citizens.

The jump in the uninsured rate coincides with a year that was otherwise prosperous, with income rising and poverty declining.

Democrats are not reluctant to pin the blame on the president.

"President Trump's cruel health care sabotage has left two million more people without health insurance, forced to live in constant fear of an accident or injury that could spell financial ruin for their families," said Nancy Pelosi in a statement.

Read more: 

• Decline in subsidized ACA enrollees driving up uninsured rate
• Who are America's uninsured?
• 10 states with the highest uninsured rates