In my limited experience in the several places I've lived in the US, only one had an issue with water that was hard enough to need addressing. Most residences there had a dedicated household water softener, so even there the dishwashers didn't need to do their own softening.
Another anecdote from the USA: I've only ever had problems with hard water in a house that got water from a well. Never had a problem with municipal water (although there are other contaminants in that).
From that link [1 above]: "An overwhelming 85 percent of the USA has hard water, so the likelihood that you live in state or city with hard water is high."
For a random location. Comparing the water hardness map with a population density map it seems that most are living in areas with soft water.
Here's a nice map [1]
[1] https://homewater101.com/articles/hard-water-across-us