As coauthor of a widely used comparative systems textbook (third edition now in preparation for MIT Press) who travels around a lot and talks to economists and policymakers in many nations, I have been struck by a nearly universal argument that has been made to me repeatedly, often with dripping contempt for the discourse in the US, an argument that they consider to be obvious and a matter of common sense as well as good economics, but that one almost never hears within the US. This is that the presence of negative externalities from having sick people walking around justifies making sure that everybody has health insurance, however one mananages to pay for it or organize it, so that people will get preventive care from physicians and not be wandering around infecting those around them. With the US being the only high income nation that does not have universal coverage, I do not know to what extent our poor showing on life expectancy (37th to 50th depending on source and how many micro states one includes on the list) is due to our failing to cover everybody and avoid this obvious negative externatlity, but I have no doubt it aggravates this poor performance.
Of course, the joke is that the new ACA (aka "Obamacare," even though it was initially a GOP-supported plan out of the Heritage Foundation implemented in MA by Romney) does not provide universal coverage, although it increases coverage. The SCOTUS in an unprecedented and supremely stupid move dramatically reduced this expansion of coverage by allowing states to opt out of the Medicaid expansion in the law, with that the leading source of the hoped-for expansion of coverage, now limited, and with the states with the highest percentages of uninsured (25% in TX) being the ones with governors or legistlatures or both blocking adoption of the Medicaid expansion. I guess we should understand that at least one reason we do not hear this argument universally used in other nations is that ACA does not mandate universal coverage, although clearly the argument can be used to support the expanded coverage under ACA. Unfortunately, I think the subtext of opposition to universal coverage is just plain raw racism, people not wanting "them," the moochers of racial minority status, to get coverage, especially those illegal immigrants who should be encouraged to leave the country and certainly should not be given any coverage, even if them getting sick puts all of the rest of us at greater risk of doing so as well.