That map shows regions exceeding 1.5mg/L, i.e. over twice the amount that the US and other countries place in their municipal water supplies. It’s not a map of

That map shows regions exceeding 1.5mg/L, i.e. over twice the amount that the US and other countries place in their municipal water supplies. It’s not a map of places with suitable concentrations of fluoride in groundwater; it shows excess amounts. To my understanding, both Switzerland and Germany have around 1.0mg/L fluoride in much of their groundwater. This puts them firmly above municipal levels in the US, but below what your map shows.