Having re-read your post, it seems that you are currently a PhD student in the UK? If so, I would urge you to think very carefully about quitting in the hope that a move to the USA will be somehow better. It may be, but the 'grass is not always greener...'. Quitting a PhD (for no good reason) is not good for your CV, and having quit one PhD, many supervisors would be hesitant to give you another chance.