I'm not 100% fluent in the US system, but it seems as though the length of time you can go before specialising is the main difference from my experience. It seems long to me, almost coddlingly long. While I didn't know what I wanted to do for certain when I went into A-Level, I did know the general field. I find it hard to believe that someone beginning college actually doesn't know what general things interest them for the most part. I'm having trouble wrapping my brain around the idea of a person who can't decide whether it's English Literature or Engineering they want to pursue, they're poles apart.