Even when it was The Holy Roman Empire there was still a region of Polska known as Polska (they still don't call it "Poland" in Poland). Here is a map of the region in 1000 AD.
There was a hundred twenty something year period when Poland did not exist as a country, from the 1790's until the end of WWI when it was reestablished as a nation. Poland's Independence Day is Nov. 11, Armistice Day.