Gettysburg is in Pennsylvania. A battle took place there that turned the tide of the American Civil War towards the Union's(North) favor. I think most Americans should have a good understanding of something so important to their history. If someone in say, Canada didn't know, it wouldn't be a big deal. Why would they have to know?
And yes, there are many American kids who don't know Soviet Leaders, nor could they identify the fmr. USSR or Poland on a map. (hell, most of them probably couldn't find France...) WWI and WWII is taught in elective classes, but not the required World History or US history. (at the honors level, they are) I took a 20th century world history where things like WWI, WWII, the Russian Revolution, Cold War, Cuban Missle Crisis, etc. were taught in great detail.
There are extremes in the American educational system. There are those who really care, make a point to learn about things other than sex and drugs, and those who don't care. It aggravates me more to be around a person who doesn't care that they don't know, than someone who just doesn't know.
If Americans knew more about different countries and their history, they'd be less hasty to make snap judgements against a group of people. (i.e. the backlash against Arab Americans after 9/11) Too many Americans are ignorant of the world around them.