I'm not exactly sure what you mean when you refer to the Anglo-American culture of the United states. What specific values are under threat?
First, let me say that I'm not in favor of dumping Anglo-American culture. It's a boat that floats--successfully--even though it needs patching and some course correction. And Anglo-American culture is the major ingredient of black American culture.
But as I've said multiple times before in other threads, the Democratic Party leadership is enthralled by Critical Thory ideology, specifically Critical Race Theory, Radical Feminist Theory, and Critical Gender Theory. The common platform of each of those three is to destroy the culture of the "Oppressor," with the Oppressor of Critical Race Theory being White/European culture, the Oppressor of Radical Feminism being male culture, and the Oppressor of Critical Gender Theory being heterosexuals.
As confusing as it may sound, the Democratic Party Leadership supports efforts to do all three simultaneously: Demolish White/European culture, demolish male culture, and demolish straight culture.
To MAGA, that means demolishing Anglo-American culture, and they are not paranoid, that's what's being pushed.
This isn't surprising when you look into Critical Theory and see that they proudly proclaim their basis in Marxism, and thus share that same Oppressor/Oppressed class warfare basis of Marxism.
It's why, during the Chinese Cultural Revolution, physicists were murdered because "physics is Imperialist." In the same way, you've got people in the US using CRT to show "math is racist" and "English is racist" and even "punctuality is racist" because those are all elements of Anglo-American culture.