I am completly opposed to Air-conditions propagandized as a solution to climate change. What is the wright approach to combating this state of temporary relief except from old-fashioned fans? Don’t get me wrong. They do the job for me. I am reffering to finding a solution for people more with health issues or large facilities that are in need of something more drastic.
Building anything underground is extremely expensive and energy intensive, as you have to constantly pump ground water and pour concrete to keep walls from breaking under pressure of tons of soil.
So yeah, underground could work, but better used sparingly when benefit outweighs the costs, like maybe in areas that could go literally uninhabitable on the surface. Otherwise not worth it.
Most of North America built bungalows after WW2. All your dramatic concerns were addressed 50 years ago, and no, they were not extremely expensive and 8" concrete walls with French drains and sump pumps work well.