In the US, they seem to exist in offices and schools. Airports tend to have them, and often with a bottle filler on the side, which is great since we can't carry water through security.
But, just walking down the street, truly public water? Is that a thing anywhere in the US, or elsewhere?
More and more the newer ones are also "dog watering stations" which is basically a foot-operated drinking fountain with a slow-drain bowl (or just a concrete bowl with no drain).
Even parks that don't have restrooms will often have a fountain.
I'm struggling to think of any parks or high pedestrian areas around me that don't have a public fountain, nor in any of the cities I've lived in. Like, yeah, you're not going to have a fountain out in the middle of a parking lot. But they, to my recollection, seem to be everywhere that people tend to be walking a lot.
As for Europe, they also tend to be in a lot of high pedestrian areas, but really only in southern Europe (Italy, Spain, etc). In northern Europe it seems that everyone is just fine with being constantly dehydrated.
The park across the street doesn't have one. There are none in the town center (gotta buy Starbucks or similar).
And I don't recall seeing any public ones in downtown DC, other than the Mall and Smithsonian areas.
I already stated they do exist in quasi-public spaces (airports, offices, etc).
Like, if I'm running errands downtown, and I'm not in the tourist zone, there really isn't much without ducking into an office (that might be locked on the weekend).
Maybe a state level law thing then.