Since I never drink American tap water, but instead always buy bottled water, I'm actually surprised to see any country being listed as undoubtedly safe. And, judging from bottled spring water flying off the shelves, it appears that others are reluctant to drink tap water as well.
And I was drinking bottled water exclusively even prior to recently finding out, as we all have, that Camp Lejeune had badly contaminated water during the entirety of my "stay" there between 1977 and 1980.
Of course, part of the time between 1977 and 1980, we were on "cruises" (quote unquote...our sleeping racks were five high up to an 8 foot ceiling, about 40 men in a 10x10 room) during which we were transported to the Mediterranean and Caribbean for combat training. So maybe during the six month Med cruise and the two month Carib cruise, the Navy ships had good water which we used to fill our canteens. But I doubt it.
So let's not look down our noses at other countries' allegedly bad water. In my opinion, our water ain't so hot, either.
Moreover, I think it's overly simplistic to do a black and white analysis in which the conclusion is that an entire country has "good" water, while another has "bad" water. Few things are that black and white and are instead more nuanced.
For example, I participated in a summer university program in Mexico soon after my Marine Corps discharge. There were university professors teaching courses, and other university-affiliated scientific researchers trying to understand the "turista" phenomenon. The latter's conclusion: it's not the water that's bad (as everybody thinks), it's not the water that causes the severe debilitating abdominal cramps and non-stop diarrhea, but instead the outside of fruit and vegetables that have the pathogens. So if you can't peel the fruit and discard the peel, or you don't cook the vegetables, don't eat them.
That was apparently true in Cuernavaca, Mexico, but their research was focused only upon that city.
So to be safe, bottled water is the way to go worldwide, in my opinion.