Applying to an American medical school from the UK? (2017 entry)

So I really want to do medicine, but I don't know about studying in the UK, but I don't have enough knowledge about studying in America. Would anyone be able to give me some insight into how I would go about going to an American university to study medicine?

GCSEs: Maths = A, History = A, ICT = A, Statistics = A, Art = B, Further science = A, Core science = B, Additional science = B, German = A, English language = B, English literature = A*, RS = A*.

I'm in Year 12 now, and I am taking Biology, Chemistry and German for ALevels.

American universities only do postgraduate medicine, and it's stupidly expensive if it's not Harvard (they offer huge bursaries). As a general rule, American universities like very high achievement in extra-curriculars in addition to top grades, so I don't really think American unis are worth it for medicine if you don't already play for an olympic sports team or play 10 instruments, and have unlimited money.