The development and use of the local norms may indeed be beneficial for people all across the United States of America along with the rest of the world as well. These local norms may overall help many different people all across the world. It can better help with traditions and other things.
There is no guarantee that local norms are beneficial, but they certainly can be. Primarily, they can create a sense of community, place, and interrelationship that strengthen the cohesion of a group, and make life more stable, predictable, and understandable. This is beneficial at the very least to the group in question, though there is certainly the possibility of creating norms that are also harmful to others.
I do not believe the development and use of local norms is beneficial. I know politicians try to use this within the United States and I find it very rude. I believe areas are culturally diverse and people tend to move around and these local norms don't always represent the population.
No, the development and use of local norms is not beneficial, because it is hard for people who are not from the immediate area to figure out how to function. The person ends up being left out, ostracized, or criticized, because they do not know how the locals do it, and the locals assume that the person should magically know.