I don't think I have the wrong idea. Obviously Kentucky doesn't have the healthcare system of France, Sweden, Finland, et al. And it doesn't have the overall top tier welfare state system of Finland. This is understood by everyone on this forum.

Even if you gave Kentucky universal healthcare and pumped up the social safety net, I think it would take a lot more than that to match the overall quality of life that a Finland offers. That includes everything from culture to architecture to crime / murder. The same is true of other elite outcome nations like Japan, New Zealand, Sweden and Denmark. Maybe Kentucky could develop that given time, or maybe it remains a Greece, Portugal, Hungary or Bulgaria of the US, a lower tier economy state vs the elite outcome states. The poorer nations of Europe usually have normal, functioning welfare states, free education and universal healthcare; it doesn't by itself do much to put them up with the better economies, as so much more goes into it. There's a strong argument that the geographic nature of Kentucky alone might be enough to permanently trap it in a lower tier condition.

My argument is that the only reason relatively backwards states like Arkansas have GDP per capita figures like France and the UK (preposterous on the surface), is because they're heavily free riding on the immense output condition of the US as a whole. I think it's quite obviously true.

The US has a homelessness and poverty rate like Canada. It has free healthcare for the bottom 25%. It spends as much on its welfare state as a share of its economy as Australia and Canada (and rising). Most of its $7.x trillion in government spending goes to welfare state programs / social safety nets of one sort or another. None of that properly explains why Arkansas can have the output per capita of the UK or Japan. The only thing that explains it well, is Arkansas gets to ride the US $62,500 GDP per capita figure (they perform at a subpar level, so their per capita output is 1/3 lower than the national figure). They get innumerable benefits from being part of the US, in terms of the USD standard, smooth national cross border trade, energy supply, military protection, federal subsidies, and so on. Kentucky for example is the third most dependent state when it comes to federal money. Those are pretty huge system benefits that few countries will ever get to experience.

What you de facto have, is states like Washington, California, Illinois, Virginia, New York, Massachusetts, Texas, Colorado, et al. heavily carrying states like Kentucky or Arkansas. If you're in Europe, and you're N.Macedonia, Ukraine or Serbia, Germany is not doing very much at all to carry you by comparison. And if you're Bulgaria, Hungary, or Croatia within the EU, the same is still true, only to a lesser extent (which partially explains the huge gap in economic output & development between EU nations, far larger than the gap between between US states; Bulgaria has been a member of the EU since 2007, yet their per capita output has barely climbed since 2008, ie hasn't narrowed with the far wealthier nations; the same is true of Hungary, they've seen very little net improvement or narrowing since 2004/2005). US states by comparison have it exceptionally good when it comes to the way they get to ride the overall US economy and its various perks.

Without being part of the US system, I think you'd see a far more dramatic divergence of outcomes among US states. You'd get the nations of Arkansas or Kentucky with a GDP per capita of $10,000 or $15,000, in the same manner you see that type of large divergence in outcomes in eg Europe and Asia.