They’re the constituency that supports Trump.
Numbers like GDP or total wealth will be highly misleading — and it’s unsurprising that the opinion of the petite bourgeoisie (who primarily make up HN) differ from those groups.
When the party advocating wealth redistribution also calls them “deplorables” and flagrantly provides worse services (eg, NC disaster vs CA disaster) that seems like a reasonable belief.
There's no dispute that America has become incredibly more rich and powerful over the past 40 years. The fact that that money is increasingly funneled to fewer and fewer people (as a percent of the population) is something that can be changed locally, without changing our foreign policy stance.
It's not a surprise that the "devastation" of the middle class coincides with the continued reduction of tax rates on the entities collecting all that money. The America that MAGA seems to think was great was one of higher taxes and more social programs.
The manner in which those people accrued wealth is deeply related to the issue, by subverting the working and middle classes domestically.
I understand that many of the petite bourgeoisie believe that destruction of those classes via internationalism is a means to usher in communist policy — but that’s opposed wholesale by the American working and middle classes.
You're still describing economic policies though, not diplomatic ones, and while they're not entirely disconnected, trying to fix international economic issues by burning down alliances is likely to result in a lot of negative second order effects while not even addressing the main economic concerns.
If we're ascribing bad faith motivations to particular viewpoints here though, I'll point out that conflating concerns about trade policies with the idea that America should entirely abandon any interest in the rest of the world is enormously helpful to countries that would like to pursue far more aggressive imperial ambitions currently being blocked by American power. Having rightfully angry people in America's rust belt become convinced that the only way to revitalize the industries that used to power their cities is to let Russia reform the Soviet Union has got to feel like the political victory of the century to Moscow.
So "leaving money on the table" is admittedly very vague, using it here I'm principally referring to two things:
1) For many decades we've had a trade posture and foreign policy regime which emphasized moving production offshore. This generated a lot of corporate profits and some consumer benefits but was absolutely decimating for working class incomes and job prospects. We "left money on the table" here in the sense that money which would have been generated in the US and paid wages in the US tended to end up mostly in the hands of wealthy people in poor countries (and to some degree in the hands of their middle classes).
2) The other way we left money on the table was by opening up our markets to countries which didn't reciprocate in kind -- we reduced our tariffs on them, and they didn't reduce their tariffs on us. This again encouraged the flow of production, jobs, capital etc. out of the US and again hit the most vulnerable economic classes hardest.
The net result of this is that we have a lot of money in the US in a record few number of hands -- when you add corporate consolidation & monopolization to the mix you have a pretty complete picture of why a lot of people in this country are struggling.
So did we benefit from these policies, yeah, we did in certain ways that accrued particularly toward the top of our economic pyramid, but it seems that the bottom of it has had just about enough of this and is getting loud about it at the ballot box.
I'm not sure America actually has left a lot of money on the table. I see America having benefitted a lot from the post cold war world order (as indeed have most of its allies), and my take is that the kind of extraction of value that Trump has been attempting is at very best only beneficial in the short term.
But again, I appreciate when people with different viewpoints can discuss them civilly, so I gave you an upvote.