> The US is 5-10x larger in population than the other single-payer-ish systems usually cited.
Which doesn't explain the vastly higher per capita (and even per GDP) costs.
> Also, we in the US tend to have bigger problems running giant federal bureaucracies
That doesn't explain why the US costs (again, per capita or per GDP) are still higher than the total costs in many countries providing universal coverage even if you exclude the slightly-less-than-half of US spending that is public spending.
> Our existing single-payer-ish health bureacracies, like Medicare
Medicare isn't single-payer-ish, as for decades there has been policy to move from traditional single-payer-ish "Original Medicare" to (usually partially, with a personal premium as well) publicly subsidized private insurance "Medicare Advantage" plans.
> These smaller systems also benefit as free-riders from positive externalities thrown off by the United States' eccentric overexpenditures - like drug and new-treatment beta-testing.
Er, a lot of drugs and new treatments are tested and accepted overseas before they are in the US.