Earlier quoted context omitted.
Risk pools in other countries work pretty well, and their populations are Denmark’s population is that of Wisconsin. The least populated state (Wyoming) would have a larger risk pool than Iceland, which seems to be doing fine.
Sure. For that matter, some bigger corporations in the US choose to run their own. But it is just math - bigger pools have more resources over a larger population, and so are better positioned to survive shocks.
My point is that you can have adequate risk pools at a lower administrative level (the states), while not having to deal with having to build up political will among a large, heterogenous polity.