Rich Scandinavian countries, for example, have a more redistributive tax system that appears to leave people broadly happier. Fine to argue the relative merits of such an intervention, of course, but worth noting it’s very much an option.
Apples to oranges.
I don't see why scale would matter that much. If it works for 12 millions why wouldn't it work for 2times more, or 10 times more ? Or 30 times more ?
It would require some real argument about why size matters and prevents the policy from working. Because right now the US has an economic repartition similar to Israel, which is even smaller than Sweden.
Of course the Nordics are smaller than the US, but all of the economic variables in question should scale on a per-capita basis. Specifically, what is it about a population difference that makes a strong safety net inapplicable?
Except it's baloney, the EU even has a bigger population than the US and has universal healthcare, public transit, etc.
In doing so, many countries with these sorts of nation wide programs may become woefully uncompetitive, not to mention quality of services would go down.