"The God who made the world and everything in it is the Lord of heaven and earth and does not live in temples built by human hands. And he is not served by human hands, as if he needed anything. Rather, he himself gives everyone life and breath and everything else. From one man he made all the nations, that they should inhabit the whole earth; and he marked out their appointed times in history and the boundaries of their lands" ~ Acts 17: 24-26.
Yes, God made all the nations and he marked out their appointed times and boundaries. Poland is for Poles, by His Divine Order. At least that is how I feel about it and like it very much. Why? Because, it such an atmosphere offers a true sense of belonging, a true sense of identity that is deeper than a social contract. Yet, the Lord did send Abraham to a 'promised land'. Did he integrate? For those times and place, he did.
"In the cave that is in the field of Machpelah, which is before Mamre (Hebron), in
the land of Canaan, which Abraham bought along with the field from
Ephron the Hittite for a burial site. " There they buried Abraham and his wife Sarah, there they buried Isaac and his wife Rebekah ..." Genesis 49: 31.
So, Can anyone become a Pole? Why not. You can become Polish by language acquisition and cultural practices and labels, traditions, customs and or religion.
People have migrated from here to there, as in from place to place, either by will, appointment or seeking refugee and or new life. Once there, in that 'promised land' they became of that land, place and culture. Call it a melting pot but don't call it multiculturalism or pluralism. Such isms belong outside of the real pot, or parallel. Because, if you want real assimilation, if you want to be part of the group, then you have to join in, take up the same yoke, ideas, desires, goals, and all past burdens, histories tragic and victorious as yours.
That is what it means to integrate!