I think there might be, if your selected list of Universities will accept AP/HS Diplomas as equivalent. The standards of education is quite different and you might find Universities aren't all equally accommodating, so you might really be missing out on some good courses.
It's quite late this evening, but by tomorrow morning it's never a bad idea to phone some Universities you intend to go to and explain to the admissions tutor(s)/departments about your conundrum. I presume you're quite competent at subjects like maths/science, so you should find most of the content straightforward and won't lose a lot of time for learning/revising extra material.
English language may have controlled assessments and coursework, which can be a problem if you plan on taking GCSEs but leave it to late to let your exams officer be aware of what you want to do.