You are just doubling down.
No one is disputing that Marx was born in Prussia - and that was his nation state until he was expelled or renounced it.
What I (and others) are saying is that he was a German citizen/subject of Prussia. When NYCBlue said Marx was German he was 100% correct. You have chosen to dispute that with ever more convoluted deep dives into Wiki. 'German' was and is an identity that describes someone from Germany and speaking German (whether a united state after 1871 or after the collapse of East Germany, or whether 39 politically separate states under the Holy Roman Empire or the German Confederation). It was an identity used by and understood by people inside and outside Germany at the time of Marx's birth.
But to get back to the starting point, critics of taking the knee who allege it is Marxist (or that the US BLM organisation is Marxist) in the main do so without the slightest understanding of what they mean by Marxism. Even worse they are often the ones who bang on about something they call 'cultural Marxism' which is (I think) a meaningless confection invented by former revolutionary communists (the Revolutionary Communist Party that went on a rightward journey through Living Marxism and Wired to the Brexit Party with Claire Fox and others) to confuse and mislead people. They succeeded.