Honestly Alison, I get that we have a crap reputation, but as someone going into education I at the very least have to point this out.
Every state in the US has a course of study with specific standards for each grade in each subject, in addition to National standards for each subject. The states' courses of study can vary-one thing may be taught in one grade in one state, and in another grade in another state, all the way up through high school. It's not really fair to assume teachers in America don't want their students to know anything about other countries. If they actually follow the curriculum correctly, they learn geography and the standards themselves are not typically lacking content-rather, they might not be followed correctly.
Also, I think people don't care to remember what they learned because as individuals, they decided it is not important to remember.
But really, my point is, things can vary so much by region that I cringe every time someone talk about "America's schools". And believe me, I have had my fill of reading books and articles about how crappy we are and everything we are doing wrong from my courses. The odd thing is, very few people bother to explain how to fix it. The fact is, I think it all depends on the teachers. It's the philosophy. You have to want your kids to learn about the world. You have to integrate in in other subjects. You have to make the effort. Good teachers don't let their students become ignorant...but students themselves sometimes choose to be, even after they have been taught. I really think a lot of Americans you have encountered that seem ignorant may well have been taught Scottish people speak English but they cared too little about it to recall it.
One of the big problems is that with No Child Left Behind demanding standardized testing, teachers end up teaching to tests and the students forget everything they memorized to answer test questions.