That is the uniform culture. You see it in tv shows everywhere, people looking the same in every show etc. (the 1 black, 1 white woman 1 white man 1 Hispanic 1 Asian group you see everywhere in American stuff)
There used to be shows like Friends and Fresh Prince which means diversity, now everything is just the gruel of the melting pot.
It does rest that cultures will become homogeneous over time as they melt together but I take what is being asserted to be different from that, as in it’s promoting an artificial uniformity of culture rather a naturally blended one
Yeah, it feels like instead of enabling a diverse set of cultures to coexist they try to enforce a culture that has a diverse set of things in it.
Feelings being what they are, you can't really 'disprove' them per se, but this may be more of a reaction to media representations of diversity vs actual ideals