American's educational system isn't all pick and choose. Once you get to the high school level there is a set of paths you can choose. For example, with Science the path's look like this:
Bio 1 - Chem 1 - Bio 2 - Elective
Bio 1 - Chem 1 - Chem 2 - Elective
Bio 1 - Chem 1 - Physics - Elective
General Science - Bio 1 - Chem 1 - Elective
Electives include: Bio Chem and Organic Chem, Anatomy and Ecology, Chem 2, Bio 2, Physics, and Scientific Research. You can not take a class that you have already taken. There are also honors classes that take the place of the normal class. These are AP Bio 2, AP Chem 2, and AP Physics. It is also possible, if you have the time in the day, to double science. For example, I did Bio 1, Chem 1, and this year I'm doing AP Chem and AP Bio. Next year I'll do AP Physics and the Research Course (2 electives).
That's just a sample of a more complex branching system. It's not so much we get to chose what we want. We have to have so many years of English, Math, Social Studies, Foreign Language, ect. to graduate. We can chose what course within a certain field to take however, at certain points.
In Social Studies, there are core classes for 3 years, and then an elective. By high school there is no Geography class - it's integrated into whatever your studying (US History would have US geography in it; World Cultures, world geography; European History, European geography, ect.). It's also integrated into the Elementary and Middle School cirriculums. However, Americans are deficient in Geography, as well as other schools. There was an foreign exchange student in my US History Class, and she had a 97 average - top in the class. It was really embarassing.