@Strandjunker - this is a bad take.
First, ICE is capable of running camps in the US, for example on military bases.
Second, Auschwitz and hundreds of other concentration camps and two death camps were located in Germany proper, the other in Greater Germany - see the map below. Auschwitz was part of Germany proper from 1939 to 1945.
Third, unlike El Salvador that has full control of the prison/camp on their territory, Polish government was in London and had no control over the camps.