Modern economic theory is a fig leaf over the raw reality of resource allocation. A better fig leaf than most, but still a fig leaf. In particular, there are many macro metastable equilibrium points, post-WW2 middle-class America being the exception rather than the rule. Fewer people, true, but with vastly higher purchase power than the masses.
Considering how high American incomes tend to be compared to the rest of the world, this seems like a culture of spendthrift irresponsibility.
Meanwhile, the rest of the developed Western world has the government provide healthcare, pension systems, actual sick time that also accounts for longer periods, public transport so you can get away without a car...
It's a cultural issue.
To use a 200 year old quote: "They should eat cakes instead".
Someone with absolutely no money to spare absolutely cannot set aside 10% of their income - and even if they manage to do so, it's all one healthcare or other emergency away from being wiped out.
We are already seeing this outcome. About 2/3 (!) of Americans live paycheck to paycheck [1], 56% of Americans have less than 1000$ in liquid savings for emergencies [2]. In Europe, the situation is better because we have somewhat decent social safety nets, but not that much (e.g. in Germany, thanks to inflation, record numbers of people depend on charities like food banks [6] which are essentially funded by donations from large supermarket chains).
At the same time, a lot of the largest employers [3] in the US - especially Amazon, Target and Walmart - stand to benefit massively from automation gains... meaning that a lot of their staff will be made redundant as technology improves. Amazon is continuously investing in warehouse automation to replace human "pickers", and supermarket chains are investing in automation e.g. to spot spills [4] or monitor shelves for stuff out of stock [5].
Individual companies are not to blame for this per se: capitalism incentivizes a company to reduce costs wherever possible. The answer to the resulting shift of profits and wealth, however, must be in politics - and to be honest, if the wealth gap keeps rising with people like Bezos or Musk being worth hundreds of billions of dollars each while the 99% lose their homes and die because they can't afford basic medicine like insulin, if politics don't do anything, social unrest will only keep growing. Occupy Wall Street, the 2016 election of the 45th, French Yellow Vest protests - they all were, at their core, protests against this wealth disparity, against the effective neo-feudalism towards which we have devolved.
And to make the situation even worse than it already is: taxpayers worldwide will have to pay down the enormous bills from COVID relief debt and investments to combat climate change (e.g. constructing new power grids and renewable-energy plants), the followup costs of the Russian invasion in Ukraine and potentially a third world war - but there is no sign at all in any Western country that the rich will pay their fair share for all this crap.
[1] https://www.cnbc.com/2022/05/11/two-thirds-of-americans-live...
[2] https://www.cnbc.com/2022/01/19/56percent-of-americans-cant-...
[3] https://largest.org/misc/employers-usa/
[4] https://mashable.com/article/stop-and-shop-marty-robots
[5] https://www.roboticsbusinessreview.com/retail-hospitality/5-...
[6] https://www.tagesschau.de/inland/situation-tafeln-101.html