What works well outside of the US is that the single-payer government run (or at least government mandated) provides a standard level of care, which more often

What works well outside of the US is that the single-payer government run (or at least government mandated) provides a standard level of care, which more often than not includes wellness and life threatening care (and a lot in-between), and one can buy additional coverage in the private market - but the basic standard care is considered a right, and doesn't disappear just because you have some additional coverage.