Blame the fragmenting US population identity-wise, which has been accelerated by rhetoric on the left. Fewer and fewer people identify as an "American" with each passing year meaning that it is harder and harder to push policies that benefit "Americans".

I lived in China for 1.5 years in 2005 to 2006 and culturally, once you pull back the facade of language and food, it wasn't terribly different than how America felt in the 80s (earliest decade I can remember and the last decade where there was still a semblance of cultural uniformity and support for pro-America policies)