So the idealistic approach is that "sure, everyone should have a better life". The practical approach is that "I have to pay from my own pocket for some lazies have a better life". And when you put it that way it suddenly looks a lot like "the average person doesn't want a better life for all".
Frankly, it's unlikely there is such a citation, but that doesn't mean OP is wrong - just consider whether there's some class of people you feel negatively about (billionaires? homeless? immigrants? republicans? democrats? criminals? violent criminals? etc) and then ask yourself the question "do I want THEIR lives to be better?"
And if your answer is yes, then ask yourself "am I willing to sacrifice any of my own wealth or comfort to make that happen?"
And if your answer is yes again, then ask yourself "do I think the average American would say yes to the first two questions?"
For example, I can say with all honesty that I don't feel the lives of American billionaires need to be "better" in the abstract - they're doing fine, and they'll continue to be fine regardless of what I think or do. In fact, I want their lives to be worse - insofar as I believe they should contribute more of their wealth to the common cause, and I agree with the argument that less wealth is "worse" than more wealth in most ways.
So, while if there was a poll that had asked a representative slice of the American populace "do you want a better life for all?" sure, most people might say yes. But with a more specific question, for example "do you support the death penalty for a person convicted of murder?" fifty-five percent say "yes, the death penalty is acceptable" - which is apparently the LOWEST level in fifty years! So clearly there is at least one class of people (murderers) for whom it is the majority viewpoint that their lives should not only be worse, but ended entirely. No doubt others could be found.
[1] https://news.gallup.com/poll/312929/record-low-say-death-pen...
Such a citation could be a link to a poll or something.
You made countless other claims I disagree with such as "But a significant minority of the population wants a WORSE life for the black population." (where I doubt the "signifant" part) but it's considered poor form to put a citation needed after every sentence so I'm going after what I think is the most objectionable claim that maligns 160+ million people. Even if I do think your black and white (do east asian americans not exist?), oppressor and oppressed viewpoint is demonstrably false (though with more effort than you or I can spare now).