It's really not that complicated though. Our houses easily support air-conditioning, what the hell are you talking about? If anything, our houses are better suited as they are insulated really well. Just cut a damn hole through the wall and install a split unit.

We're just not used to it and until now it was considered a waste of energy. That's it.

The house I live in is cold as fuck by the way. And I don't have an AC unit. I just don't open the doors and windows during daytime. At night I let the cooler air in. I do live in the northern part of Germany though. That may not be viable for you.

You drill a single hole into an exterior wall and you mount a mini split system. You don't need to do central air systems to have AC, in fact I think the consensus is they're less efficient for individual homes and flats.

In Germany, and I assume everywhere else, the largest issue is landlords have no incentive to take care of their properties past maintaining it from a sellable perspective. Never in my lifetime has one of my landlords voluntarily made the living conditions of their property better. The moment it goes into law that homes have to be cool able down to 24° (like we mandate for heating in the winter) or landlords are outlawed (thus allowing everyday citizens to improve their homes) AC becomes a very solvable issue. I'd have installed AC in my last two flats if my landlord had let me even just take it out of rent. But no, absolutely no reason to reinvest in a home you don't live in and plan to use to supplement your income.

If it must change it might be cool to have a blade runner vibe where old buildings are retrofitted with futuristic technology.