Altitude has a significant affect on engine performance [1], regardless of your opinion on transmissions. Conventional wisdom dictates declining carry capacity per altitude gain. "Note: For high altitude operation, reduce the gross combined weight by 2% per 1000 ft. (305 m) starting at the 1000 ft. (305 m) elevation point." [2] As does incline, which if you read my comment carefully you will notice I mentioned.
I'm not sure you're an authority on what folks in the American Midwest are or are not towing with cars, but I will note that automobiles in North America have one rating, nationally. There's no regional tow rating for Rockies vs Flats, or cold weather performance in Montreal vs Florida.
As with most all things in life, the answer lies in a complex host of variables, not just one singular difference. Just trying to be informative, there's no need to be defensive.
[1] https://www.aamcocolorado.com/high-altitude-car-maintenance/ [2] https://www.cars.com/articles/should-your-pickup-tow-less-at-altitude-454166/
The entire "Organize the store by Brand(TM)" rather than by product is a terrible consumer experience. Truly a horrible idea made by horrible profiteers.
Want to compare and buy an SD card? You need to go to the SanDisk section, the Samsung section, and the Other Misc Junk section. And btw the sections are on opposite corners of the store. Ain't nobody got time for that.