There is so much misinformation and disinformation around single-payer Medicare for All (M4A) that sometimes it becomes hard to compare M4A to the current United States health care system or the other broad categories of proposed health care systems. Other than M4A, there are only really only two other types of proposed health care systems, an improved ACA and the public option.
The link provides a summary of how current and proposed health care systems compare to M4A: Health Care Systems Comparison.