Fluoridation is by no means universal in the US—around 69.2% of public water in 2006, according to Wikipedia[1]. In some areas, resistance is strong and cuts across diverse political orientations. Portland's 2012 attempt to fluoridate, for example, drew opposition on the basis of libertarianism, environmentalism and science skepticism.
[1] https://en.wikipedia.org/wiki/Water_fluoridation_in_the_Unit...