I wonder what the history is here. Neither the article nor Wikipedia really get into why the differences by country. Certainly, if one were to go by national prejudices, one would assume the US would be big on UHT (when in fact it's relatively hard to find) and countries that we would assume would be into the less aggressively processed food aren't. Maybe habits developed when refrigeration was less universal?

I agree with your general observations. I tend to keep some UHT packs at home as backup (as well as hotel-type half-and-half portions). But I would never use them on a day-to-day basis especially to drink straight.