There are practical reasons why it isn’t widespread:

1. Energy is very expensive relative to the U.S. 2. Houses are old old and retrofitting air conditioning is very difficult 3. Houses are more than 1 story with many small rooms making portable and window mounted units unsuitable for a whole house

All modern apartment buildings in London are built with air conditioning because a central air system and district power make it cost efficient.

If you visit a hot place like Dubai or Bangkok, there are endless indoor malls with air conditioning that serve as a place to shop and a third space. Much of Europe doesn’t have that.

The U.S. specifically is also very car-centric. You walk out of your air conditioned house into your air conditioned car and drive to your air conditioned mall. Much of Europe… isn’t. People walk, you can’t avoid the heat.

Yes, certainly, there is a cultural resistance to air conditioning but adding air conditioning to homes isn’t going to stop people dying, homes are the least consequential part of heat in day to day life. Health advice in a heatwave is pretty much: don't go outside.