Yeah, some serious theological writers have advanced the notion that racism actually became foundational in American Protestant Christianity for a very long time.

We can tend to poo poo this notion by observing that many Protestant Christians in the North were abolitionists. We forget that many abolitionists remained racist segregationists, usually on religious grounds. Many of them were as likely to preach the curse of Ham as those defending slavery.

Most abolitionist did not not support equality, and were even less likely to support racial integration. Many, like Abraham Lincoln at first, believed Black people in the United States should be sent to Africa, and the reasons for that were usually religious. They claim God had set the races apart for a reason and that men were wrong to try to change God's intent.

White American Christians, as you suggest, tended to see themselves as special and set apart, a new Chosen People.

That's the foundational part of American Christianity I was referring to.

The new Chosen People thing survives today in Christian nationalists. The racism is still right there, directly under the surface, though people are less likely to talk about it than when I was a boy.

The Curse of Ham is mostly no longer a respectable teaching in church, but its inertia carries many white church people along, even if they are not conscious of it.