There's a name for it, episode 2

Is there a word for that thing that happens when a whole bunch of people who used to do things* slightly differently start talking a lot more and then the doing of the thing gets to be more and more the same? Or at least the differences become hierarchical and some may even be stigmatized?

"Things" can be all sorts of stuff, but mostly I'm thinking of abstracts such as ideas, stuff that's harder to pin down than (say) a recipe. The status elevation and increased spread of what we now think of as the generic USian accent, at some expense to other USian accents, via television and radio -- that's a great example of what I'm trying to get at.

I feel like sociology must have a simple word for this but I don't know how to search for it.