Some Anglosphere countries (USA, Canada, Ireland, Australia) love to add fluoride in water. They say it’s good for people’s dental health.
Europeans (Germany, Finland, Italy, France, Netherlands, Switzeland) think it’s wrong/unethical.
There is actually regular controversy around this
https://hsph.harvard.edu/news/fluoridated-drinking-water/
Do they put fluoride in your drinking water ? Are you happy with that?
It probably doesn’t matter very much, given that the four countries you listed aren’t exactly having problems because of it.