Iron Curtain was a political, not cultural border. Western civilization usually includes all European catholic countries, i. e. also Poland. (Huntington is a notorious example)
Only person I know to try to actually sit down and draw civilization borders was Huntington and put the Orthodox on a separate but linked civilization to the Western world, but even he admitted that's arguable.
It’s no coincidence that the term “Eastern Orthodox” is widely used for that communion of churches; while the Orthodox world is still traditionally considered part of Christendom, it is still distinguished from the “West”.
One of the classic dividing lines between East and West, the Hajnal line, goes straight through modern Poland. It’s closer to the historic border between Poland and Germany though.
> One of the classic dividing lines between East and West, the Hajnal line
Hajnal line is pretty controversial / outright rejected by many academics.
Irrespective of whether it is true or not, the idea that this should be somehow defining the border of (Aryan) West and (Slavic/Untermensch) East was pushed by Nazis. Otherwise it's just one line out of thousands without special merit.
