The two cities I’ve seen most commonly used for these purposes are San Antonio and Salt Lake City. Phoenix and Las Vegas are also sometimes used. Most of the sites are in the western US away from the coasts. I believe parts of the upper midwest are also sometimes used for these purposes, though these areas have to contend with extreme cold (which is more difficult to deal with than extreme heat).
These are both mitigated with on-site reserves.
Sure. That doesn’t mean you can’t mitigate damage.
Not e.g. building on the Houston flood plain is one such example [1].
[1] https://www.houstonchronicle.com/news/houston-texas/houston/...
On the other hand, you better hope your AC works in the summer.
The lack of a real need for natural disaster planning feels like it's left local governance complacent about issues that would barely be a problem anywhere else. I know folks in Dallas, Houston, and Austin who have been without power and water longer from a few hours of freezing rain than folks in Florida that got direct hit with a Cat 4 hurricane. There's certainly disasters that you can only do so much prep for, but there's rigor that comes with having to prep for something that generally helps you not totally fall apart when more minor stuff happens.