Me too, but my husband and guests are clearly uncomfortably cold at my preferred 66/67, and my sister with poor circulation just about has her hands go numb.

And to what temperature do you set your AC in the summer?

For me, it depends on outside temp. The main advantage of AC is dehumidification. So if it's 95 degrees and humid outside, 78 degrees inside feels great, and keeps the AC running often enough to keep humidity down.

If it's in the 80s outside, I'll probably drop the inside temp to 76, again to keep humidity down. I rarely set it below that. 74 feels cold in my normal summer attire of shorts and a tee shirt. If we have an 80 degree day with low humidity, I'll open the windows.

73-74F, so ~23C, my limit where it starts to feel too warm.

So you're just used to cold and not heat.

The thing about the nations I mentioned is that they either barely use any AC, like Switzerland, or set it to 25°C or more, like Japan.

They embrace discomfort - most of the world does.