But in about 25 years whites are going to be in the minority in the US. In some age groups, they already are.

You are correct that it is cultural predominance in that white culture is still considered normative and desirable, something that everyone else ought to aspire to assimilate into, but that's also a part of structural racism. Up until about 50 years ago we had laws in the US that codified that white men were the normative citizen. Imagining that this way of perceiving the culture has completely evaporated just because the laws changed is pretty naive.