I agree with a lot of what you're saying. Certainly, the 70s left a bad taste in my mouth up until recently. But, was the last decades that the country was still fairly homogenous (that ended with hypenated Americans in the 80s). Excluding disco, some good music too. Personally, I think this decade is crap. I can't even think what to call it (the Zeros would be fitting).
I think the hyphenated Americans garbage started in the 70's or earlier. Blacks changed the official named of their ethnic group a few times before the "African American" label. Of course there was
"native american" and
"hispanic american" as well, and I don't think those phrases came about in the 80's. Not that a "homogenous" society is all that wonderful, assuming there really is such a thing in a country of our size.