It's not that the culture has been entirely eradicated, but rather that it has become the dominant culture which is then exported to many parts of the world. Just compare how people spoke 50 years ago to today, in one example. Slow changes that may seem otherwise natural, except they always trend in a negative direction.

Are they still teaching homer and shakespeare, or has that been deemed racist and turned into a diversity Disney movie? Again, not exclusively in the US, but it's pretty easy to see how standards in schooling have dropped year by year since I left. I could see it dropping in real time in the lower grades as I was leaving school some 20 years ago.