During the ceremony to present the Medal of Freedom to (among others) the late Georgetown professor Jan Karski, who had been involved in the Polish resistance to Nazi occupation during World War II, President Obama used the term "Polish death camp". This choice of words was hardly noticed by most Americans, but over in Poland, shall we say, gniewają się bardzo. (They're really pissed.) As some in Poland have pointed out, the death camps were not Polish, but were established by the occupying Germans.
Read the story at the Buzzfeed.
Full disclosure: By ancestry, I'm 1/4 Polish. I have some knowledge of the Polish language, but not enough to effectively translate the quotes in the Buzzfeed article. I have visited Auschwitz, including the Birkenau unit, which are in and around the Polish town of Oświęcim. A few years back, Obama said that his uncle was in an American brigade that liberated Auschwitz, which is impossible because in reality Auschwitz was taken from the Germans by the Soviet army. He later corrected himself and said that it was Buchenwald.