If our country had ended up more homogeneous..would that have been a positive? For Black people/For White people?
Well..anyway..here we are. An amalgam of cultures and races. To me, race is irrelevant..culture rules.
If, in fact, "race is irrelevant", why associate demographic and cultural shifts at all? Why start this thread?
Of course, race matters, and it did right from the start - racism isn't called "America's birth defect" for nothing. It's at the core of American culture and "values", values determining what is up and what is down, what is right or wrong. Opportunity has been, and will be, available for some, not so much for others. I think, you are dismissing race and racism as a driving force in far too blase a fashion, and while I find Asclepias a bit annoying at times, he adds a valuable perspective Whites don't usually get. So, in a debate involving demographic shifts, listening to him helps us all to get to a broader, more detailed picture of reality.
That said, why could the U.S. turning into a White plurality (!) nation matter? Why could it matter even though a tiny, overwhelmingly white upper crust will dominate the U.S. economy and continue to exert an outsize influence over policy-making? The reason is, of course, that Whites no longer out-vote minorities in ever growing swathes of the country, more minority representatives will vote on laws, and more minority experience will influence law-making. That experience is, in large part, one of discrimination, and there is no disputing it. We see the beginnings of that right now in a racially diverse Democratic House majority, and we should also acknowledge the high number of women running and winning. Because, next to racism, sexism is the other half of that birth defect, even though it's way less often acknowledged.
What we are seeing in the currently rampant Trumpism (there is no way to avoid current politics without losing track of reality) is the rear-guard action of a White majority losing their majority status in the foreseeable future and trying to maintain their supremacy. Whatever future shift emerges from this, I hold, depends in large part on how this is going to be "resolved". There are basically two extreme options, the Bannon "solution" of ever more stridently asserted "White culture supremacy", and then-Senator Obama's "One Nation America", as outlined in his keynote speech in 2004, emphasizing the commonalities.
There will be other factors changing culture, ranging from climate science, social media, education to technology and automation, but discussing these without the underlying theme of racism and the implied unequal distribution of resources is faulty, at best, and might even miss what the future holds entirely.