The Simpsons has been known to predict the future at certain times: the Siegfried and Roy tiger attack, smartwatches, Disney’s merger with 20th Century Fox and, perhaps most famously, the Trump presidency. But there are some things the show got intentionally wrong, too, one of which was a map of the Soviet Union. In the last episode of Season 25, “The Yellow Badge of Cowardge”, Kearney — one of the bullies — pulls down a map of the USSR to cover up a betting board. The map falsely shows Sweden, Norway and Finland as part of the Soviet Union.
While Finland indeed had to cede parts of its territory to the Soviet Union during World War II, the country as a whole was never part of it or the Iron Curtain. During that same time period, Norway fell under German occupation, while Sweden remained neutral. Springfield Elementary's map of the Soviet Union was clearly inaccurate, and there may be a few reasons why. The most obvious reason is it could simply be a mistake, but it's much more likely that the incorrect map was drawn by design as a joke. But to what end?
It could be that The Simpsons universe saw a different Cold War than what transpired in ours. It doesn’t seem too far-fetched since there seems to be no evidence that the Flying Hellfish — the military unit in which Abe Simpson and Mr. Burns fought — ever actually existed. Therefore, it is fair to assume that the entire war took a different path in the show's universe – one in which the Soviet Union may have very well annexed Finland, Sweden and Norway.
However, that again seems like a bit of a stretch for such a brief gag. A much likelier explanation is the joke plays at the expense of Springfield Elementary School and its poor funding, since Kearney pulls the map out down from one of the school’s blackboards. The joke then would be that Springfield Elementary is so poorly funded that it not only uses old, but wrong old maps.
Either way, the joke is quick and can be attributed to the sharp wit of The Simpsons' writers. It probably goes by unnoticed by many – but that may be part of the joke’s appeal.