Did you read the rest of the Wikipedia article? How is better to add fluoride in the amounts the US does? It says in the Wikipedia article:

Recent studies suggest that water fluoridation, particularly in industrialized countries, may be unnecessary because topical fluorides (such as in toothpaste) are widely used and cavity rates have become low. For this reason, some scientists consider fluoridation to be unethical due to the lack of informed consent. However, a recent study funded by NHS found no significant difference between individuals who receive fluoridated water and those who don’t in terms of missing teeth and reducing social inequities.

Also, new research highlights that high levels of fluoride is problematic for pregnant women (it affect cognitive abilities of the unborn child).