No general A/C might be the case in regions that never needed it before (mild summers, cold winters), but their presence is increasing.
If anything, the AC train wreck is caused by the society being incredibly conformist and conservative, trying to cling to the world of the 20th century that no longer exists.
3 per 100,000 is a lot. That's higher than the homicide rates in New England and the upper midwest of the U.S.
In Geneva even some mobile ACs, such as mobile split units, are banned without a permit https://www.ge.ch/rafraichir-climatiser-batiment/installatio.... The only ones which are allowed are monoblock mobile ACs. Which is ridiculous given that they are the least efficient and consume way more energy than split mobile units or fixed ACs.
The problem with Europe is not El Niño. Our problem is that we are the worse region in the world in how fast the temperature is rising, as you can see in this image/page:
https://data.giss.nasa.gov/gistemp/maps/
https://data.giss.nasa.gov/tmp/gistemp/NMAPS/tmp_GHCNv4_ERSS...
We could live without A/C, and many thought that the increase would be bearable. But then we received a slap in the face, with +7ºC (+12ºF) in the western half, +4ºC (7ºF) in the eastern and north. Deaths by heat don't usually happen at someone's house without A/C: they primarily happen either to people in elderly homes without A/C and maybe even impaired to ask for help or to hydrate properly, or people working outside in sun hours. Putting A/C in every room of every home in Europe would do little if elderly homes, many of them public, are not properly adapted.
Statistics in France show that 75% of the heat related deaths happen in people 75 and older, over 90% in people 65 and older. As sad as is might sound, it is seen as a new "natural cause" of death. Hopefully those buildings will adapt.
Also, healthcare spend is really spent mostly on elderly: if you look in any given doctors waiting room, people tend to be old.
Do you have a source for this? It seems mathematically unlikely due to family sizes.
To be fair - cold air hit (I'm talking about big gaps betweet temperatures) is pretty bad for you.
Ideally you don't want the temperature in a room to be (immediately) lower than T-5°C or so.
In fact we go out of our way to experience these swings with saunas and cold plunges. I have put this up in the same category of "wet hair gives you pneumonia", but I am open to learning one way or another.