I don't know the answer to this myself, but I imagine you should find out: if you're coming from school, will you have received any acceptable qualifications?
In the US as far as I'm aware you can get by with just a GPA (which is an internal mark) and some kind of certificate of attendance to say you went to most of your high school years. I *imagine* you will require some externally assessed exams. I have a sneaky feeling that AP don't qualify as I met somebody once who came from the US having done AP and they'd taken a year out to do A Levels. Which would be weird and unusual if AP did count.
Unless you've done the IB in which case you're fine.