The map in Bart's classroom is a backdrop for his hi-jinks. The fact that the colors of the states change from cut to cut could mean that it's a new-fangled dynamic map that the teacher can use to show various data over the course of a single lesson. Wouldn't that be nifty! Or it's just lazy animation. There have been other maps in The Simpsons, including a website that shows all the countries The Simpsons have been to.