FYI, "systemic racism" is usually understood to be roughly "discriminatory treatment is embedded in the institutions". For example, if Roma get stopped by police more often, that's systemic racism.

I think you use it to mean "it played a major role in the founding of our country". Saying "there is no systemic racism in Poland" makes sense in that context, but probably not in the other, and that's why people are doubting you.