Factual error: In the scene when Leo tells president Bartlett that he is attending the concert, they refer to the Icelandic ambassador as a man. Leo says his name is Vigdis Olafsdottir, when is fact it is a woman's name that means Vigdis daughter of Olaf. During the concert the ambassador is portrayed by a man. They "borrowed" this name from Tom Clancy's novel Red Storm Rising, by the way.
Factual error: When describing the location of the "oil refinery" / missile silo, it is said to be in the Oblast Region of Russia. Clearly, some intern was asked to Google Russian Regions and accidentally came back with the Russian word FOR region. It's like saying something was in State State or County County. Also, in the same episode, Bartlett berates the Russian ambassador about people being crazy in Minsk...which is in Belarus.
Chosen answer: A really annoying innate lack of sense. My friends and family say the same thing all the time, and I'm endlessly trying to correct them. I think people just don't know any better and (ironically) couldn't care less that they're speaking incorrectly.