Ok, Econ is my minor, so lets play this game. Here are some academic papers to read which support my original claim of 40 Million. It gets even more dismal the deeper your dive.

Despite implementation of the Affordable Care Act in 2014, the U.S. health care crisis continues. While coverage has been expanded, 28 million people remain uninsured, and tens of millions who have coverage are unable to afford care because of high cost-sharing requirements

Question Why is health care spending in the United States so much greater than in other high-income countries?

Findings In 2016, the United States spent nearly twice as much as 10 high-income countries on medical care and performed less well on many population health outcomes.

NCMBI study: Abstract: Millions of people in the United States do not have health insurance, and wide racial and ethnic disparities exist in coverage.We find that, on average, Americans can expect to spend well over a decade without health insurance during a typical lifetime and that 40% of these years are spent in less-healthy categories. Findings also reveal a significant racial gap:Forty-six million individuals in the United States did not have health insurance coverage in 2008 (DeNavas-Walt, Proctor, and Smith 2009), and wide racial and ethnic disparities exist in the proportion uninsured (Institute of Medicine 2001b:98; U.S. Department of Health and Human Services 2000)