I've heard of people getting scholarships in America with sport and they were from England, but I can't really remember if that was a film or real life haha.
Nonetheless, you'd more than likely be competing with kid geniuses whose parents are wealthy and pay for them to do numerous extra curricular activities. Well, maybe not but you get what I'm saying. Scholarships are competitive, no matter what the circumstances, and I personally believe that being a British citizen will lower your chances considerably.
I don't think you'd be able to get a student loan, and I'm not sure about any other loans. I really don't know if it'll be cheaper or what, but you'll have no health insurance over there, so obviously any medical care will cost. Your parents will more than likely have to fund the majority of it, y'know accommodation, tuition fees, the general cost of living.
Don't get me wrong, it's a cool, ambitious dream to have but very difficult to achieve. Just don't put your eggs all in one basket, or you'll feel very disheartened. Extra curricular activities would be good to have, y'know a sport or charity work or something? I don't really think there's much preparation you can do.