We were hearing stuff that some Americans socially divide people by their ethnicity. I just wanted to ask online whether this is true and if there could be any concerns

Unfortunately it is true, but it’s not everywhere. Generally speaking, the larger the population of an area, the less likely you’ll experience hostility. Coastal cities with large populations are highly unlikely to give you trouble. Rural aeas with lower populations have a higher chance of giving you trouble.

We even heard things like that in some places they divide people by “skin color” and base different cultures on that (we noticed that people from America even speak and behave differently based on whether they identify as “black” or “white”) and even have schools for primarily people with dark skin or so.

Yes, segregation was a dark chapter in America’s history. Officially, segregation was outlawed, but unofficially it still happens in some areas. Some of the conservative regions are trying to go back to the days of segregation and slavery. They create laws that aren’t specifically racist, but still have that effect.

As to different cultures, we have a lot of them. Most of the country speaks English, but we have a lot of different accents that seem like a different language entirely.

I dont know German, but I would draw a parallel to various English accents in the UK. Irish, Scottish, Cockney, Geordie, and so on.

As to the way white and black people talk, I suspect it has more to do with wealth and social class rather than race. Poor white people and poor black people tend to socially isolate from one another, creating distinct accents. But it’s not uncommon for intermingling.

I have a coworker who grew up in a poor black neighborhood and he has a “black accent” (for lack of a better term). If your only interaction with him is on the phone, it would be easy to assume he’s black.