a bunch of oil tycoons could play-act as working class cattle rustlers

The meaning of the hat has shifted over time. They're not acting like cattle ranchers, they're wearing it as a fashion statement about Texas culture.

And yeah, the talk about immigration is pretty disgusting, but that doesn't change the fact that the US is a nation of immigrants, it just means they're pointing the finger at the wrong problem. I hope this type of cultural issue irons itself out, because we should be championing more immigration, not less, and we can have that while maintaining strong borders. I think a lot of the people in that region understand that (i.e. ranchers and farmers rely on immigrant labor to keep costs low), it just needs to filter its way up.

white nationalist nature

Pfft, that has been consistently rebuffed. Yes, parts of the culture are still stuck in the era that brought us "Birth of a Nation," but that's changing even in some of the most stubborn parts of the country. I currently live in Utah (grew up elsewhere), and my grandmother (who grew up here) was quite racist, but since I've moved here, I've seen a huge shift in culture here. Our demographics are becoming more diverse, and our governor is openly talking about trans causes (though still doing nothing about it), so positive change is absolutely in the works. Some parts of the country seem to be going backwards, but the overall direction of the culture seems to be toward tolerance. As old stubborn people die off, they'll be replaced with more tolerant generations. What we're seeing, IMO, is a last ditch charge to hold on to that past culture.

harvesting of talent from disadvantaged communities, the flattening and homogenizing of the content

Aside from the profiteering, I think the rest is a good thing! We're bringing culture from disadvantaged groups to the masses, which increases our overall cultural diversity. We get new role models and more general awareness, and there is usually a mix of "authentic" and "pop" varieties of whatever that new culture is, and the end result is more variety.

Dolly Pardon... Amy Winehouse... Britney Spears

Old stuff existing doesn't mean new stuff can't exist too. Old people will want to see performers they're familiar with, and the same goes with young people. It's especially interesting IMO when old and new get mixed, like an old performer performing a new song, or vice versa. That cross-pollination has value, and we're increasingly doing these mashups because they're interesting.

Eventually this thing America has built is going to break

You're probably right. All empires fall and new empires take their place. The question is how long it'll last, and what it'll look like. It seems we're going the direction of other countries getting their share of the spotlight (e.g. K-Pop is getting quite big, Japanese anime is everywhere), and I'm excited to see it. I don't know if this is the beginning of the end, or if it'll spur on another wave of change that'll keep the US on top. Regardless, I think the US has an interesting culture, just like most countries and regions of the world.