In the U.S. healthcare plans typically do not cover dental. In particular, neither Medicare nor Kaiser provide dental coverage AFAIK. Dentists are quite willing for patients to pay for services directly. They'll typically charge less than what even insurers reimburse as insurance billing is so time consuming and therefore costly. There's not much negotiating as when you pay directly you're pretty much paying market rate, unless you live in a rural area where there's little competition--i.e. no market.

Market rate in Mexico is undoubtedly lower than in the U.S., though. Speaking of Mexico, they seem to have a pretty solid public healthcare program. Maybe expectations are lower, maybe people are sufficiently contented by access to relatively unregulated pharmaceuticals and medical practices regardless of poorer outcomes, or maybe griping doesn't make it across the language barrier to American news, but it definitely seems like there's less anxiety about healthcare in Mexico.