One problem is that many Americans think they should tip in places where it is not customary.
When they do this, they are, intentionally or not, trying to change the local culture. And some times they do with the effect that those who get tips from Americans will seek out Americans to serve and ignore the local population because they do not tip.
In other cases (Italy comes to mind), Americans will tip much more than the local population will tip for the same service.
Japan, China and Australia, for example, are countries without a tipping culture.