Applying to US Universities/Colleges as an UK international student.

Hello, I'm writing to talk about applying to universities in the US, however, I'm kind of stressed. I've always wished to travel to the US and study there for maybe over a year now I'm currently entering Y12 and I believe my GCSEs arent as good getting a 4 in English Language, 5 in Maths and 44 in Science I believe this simply wont be enough for any of the universities over there and maybe even some in the UK.
Ive been thinking about applying to sutton trust when they open but again I don't believe my GCSEs will be good enough. I'm currently doing a Lvl 3 BTEC and really hope I can get all distinction star so it can make my application look good. I really don't wish to resit any of my exams for a higher grade can someone perhaps give tips or advice on what to really do