the only thing in that movie that was Polish was his last name
No, you are wrong Kowalski's surname was Polish and his noble heart was Polish too. He was racist but when he got to know his Hmong neighbors he grew to like them and he realized that their noble spirit made him have more in common with them than he had with his own family, who were Westernized and superficial, and he said as much in the scene in which he looked in the mirror. So too the ending was a direct reference to the the Polish national epic, Sienkiewicz's
Trilogy, and you don't get more Polish than that.