Apply to unis in the UK and the US but bear in mind the work involved and financial aspects. Simply applying to a university in the US takes a lot more work than in the UK, you have to write individual essays for each one and for some you have to take the SAT. Also as people have said above university fees in the US are significantly higher and their undergrad degrees are 4 years not 3, e.g. MIT's full tuition fees are about $82000 and you won't get loans from the UK government, but you can apply for scholarships. As far as I can tell from your previous posts you're still fairly young, so don't worry about it too much yet and take this time to do some research and talk to your family and school about what uni in the US would mean and if it is feasible.
At the end of the day there are very good universities in both the UK and the US so don't worry too much about which country you end up in. Apply for unis in both to keep your options open then you can think about where you actually want to go when you have offers.