Exactly why does the population matter please?

Also, those countries do not all use a single payer programs. 

Finally, I live in the UK and with the exception of those earning 6 figures, the income tax rate is not close to 40%.  Furthermore, health care takes a much smaller percentage of GDP than it does in the US.  That means that health care costs a much smaller percentage of earnings, taxes, etc. . . that means that free access to health care is actually cheaper than it would be if it were all private.  I have lived under both, and from my perspective, even with all the flaws of the NHS in the UK, there is no comparison, the US system is sycophantic and stupid, but hey it makes some people a lot of money so keep believing their bs.