Would we agree that it happens frequently enough to be classified as systemic on a national level??
Of course. It's all down to the city the department is in. If that city isn't friendly to people of color, then you can't really expect the department to be either.
I'd be shocked if a city that was friendly to people of color had an issue with their police departments. By city I'm speaking of every aspect of that city.
An example:
I lived in a city in TX that while I was in college (or around that time, been a few decades) had a law on the books that black folks couldn't live past a certain street. Racist law in a racist city. Places like that aren't exactly going to be friendly to people of color.
Now this issue isn't just for non-white folks. Plenty of departments are just as awful to everyone equally. The city I spoke of above had the worst city cops I've ever dealt with. They were rude, ignorant, and just plain angry. On the flip side, the sheriff department had the nicest people. Same city, totally different mentality. It was actually pretty strange how different they were.
I think it's just like anything else. If a company has an excellent management staff, they usually do well. If they don't, then their regular staff typically isn't all that stellar either. Or, they hire "like minded people" which can get you a bunch of douchebags in a large group. In a company that might just put them out of business when they piss off enough customers. In a police department, it breeds decades of resentment and anger on both sides of the badge. Eventually, it explodes.