You suggested a few techniques that work in a cooler environment, but trust me, Texas sized heat will laugh at your European passive cooling strategies, and probably your improperly sized mobile AC.
In the United States, the AC build out reduced heat related deaths by 75% since 1960 [1]. At the same time, you can also have a situation where increased demand for AC creates an increase in CO2 production, which creates a feedback loop [2]. So you're not entirely off your rocker. Still, evidence from the United States establishes pretty clearly that ACs are effective for heat adaptation. That said, you say it's "for the vulnerable," but where do you confine the vulnerable for months at a time when the world heats up? You're basically saying your society, as a whole, is going to be off-limits for literally months for large portions of your own population. Proper long-term planning means you need to expand out renewables enough to intercept increased heat related AC energy demand, while considering equitable access to habitable environments for everyone. It also means you need to de-stigmatize AC use, because that's ultimately going to shame people away from AC that actually need it. At the moment, you're already seeing 25,000 in excess mortality due to the heat. That is a clear signal that "too hot" is already arriving.
Incidentally, I froze my butt off at work today, so you're right that Americans have an issue with abusing AC settings.
[1] https://www.journals.uchicago....
[2] https://www.nature.com/article...