The architecture is a given (in the UK at least), since we're not building new houses at a rate that matters, and I doubt many councils can afford to make adaptation a priority. But yeah, even if it isn't as good, some of the principle ideas can be retrofitted onto old UK stock - awnings are easy (and on the older houses may have been there a hundred years ago!), shutters aren't that hard, air circulation can be planned, theoretically even recolouring roof tiles or adding a solar cope cage would help. They're certainly worth trying, though landlords can and will tell you to fuck off, and even Planning Permission might butt in if their aesthetic sensibilities are offended.

Portable AC units (plus fans, because the combo is much more efficient) have the bonus of not stepping on toes, though the ones we sell in the UK are stupid and removed the outside-intake hose - which causes a large functional problem (it draws in uncontained warm air, rather defeating the point) unless you DIY a new one on.

...hm, uh, all of which is a long winded way of saying "you're right, but the UK is damned".

In Europe, most buildings are relatively well insulated and use materials with a high thermal mass. So the building itself can soak up a lot of heat during the day and radiate it out during the night. In North America you see a lot cheaper construction out of lumber and drywall instead of brick and cement, and with modest insulation.

In North America, a brief heat wave is immediately noticed and requires a lot of work by the A/C system. In Europe, you can tolerate a heat wave lasting up to a couple days. But weeks on end? Your buildings will heat-soak and at that point it starts to work against you. Your air conditioning will run all day and all night because now the insulation and thermal mass is acting like an oven, keeping the interior warmer than the outside.

Thermodynamics has not changed in recent years. There has not been any change to the fundamentals about A/C generally taking a lot of energy to run. It is just slightly complicated because of the need to factor in the building and neighborhood in which the A/C is operating.

and may not be the case for some years yet.

The point of everything i'm saying is PREPARE NOW

This "we might not need it for some years" attitude is literally going to get people killed. You're on a bus careening out of control going "well now we might not need to press the brakes yet"

You go on and on about the wastefulness of AC but I promise you there are going to be points where YOU WILL DIE WITHOUT IT and you're not going to get that fucking HVAC put in while temps are killing people lmao