Systemic only means "relating to a system, especially as opposed to a particular part".

If you and practical most people in Poland (or a lot of other countries) have never seen or talked to a black person, that is related to the system. The way you and others have formed an opinion about foreign people, or people of different faith, or sexual orientation, that is inherent to the system in Poland.

Now, the question is, what is the experience of those likely few black people in Poland interacting with other people? Do they experience in most interactions negative prejudice, or are they only experiencing it in isolated cases, or even not at all?

The way I see it, the learning we should take from the US is, that as a member of the majority, one should avoid having a prejudice of how that experience will be. Because our n of those experiences will indeed be too small to tell. And if those people are telling us that their experience is bad, not to reject it as the exception (a few bad apples).