The tap water in Canberra, Australia is the tastiest I've tried out of the ~20-50 municipalities I've sampled in Australia, Western and Southern Europe, the US, China, Taiwan and Vietnam.

Also the US is not a third world nation, it's a developing nation. Or under-developed would be more accurate, but that's not a popular term. The US is a first world nation by definition, since first world just means the US global empire and it's allies.

Outside of Continental Europe

Oddly specific when of the 10 countries judged to have the equal best tap water quality, 4 are European islands (UK, Ireland, Iceland, Malta) and many Continental European countries score behind the US:

https://worldpopulationreview.com/country-rankings/water-quality-by-country

The US has pretty good tap water in most places. Of course there are outliers we are talking about a giant country.

While you are right to trust most tap water in Europe we also have a lot of outliers. Old plumbing being probably the biggest problem. But also the taste can be atrocious. The worst tasting tap water I ever needed to drink was in Barcelona.

Edit: and the worst looking tap water I ever saw was in Paris. (It was old pipes or something as it was brown, almost red)

Canadian tap water is generally good

Canada's is good in major cities