Financial support for UK student wanting to study in the USA

Minimal funding. Try looking at smaller places (especially faith-based ones) which might offer more scholarships to international students - the bigger and more famous places will almost certainly have insane levels of competition. Unfortunately, the same issues you would face in the US are the same they would face here: not much money for people who travel abroad to study, there's the expectation that they're pretty rich.

If you really want to study abroad, the easiest way of doing it would be to try and spend a term/year in America (normally in your 2nd year); you often don't pay international fees (you pay fees to your main uni, which in turn pays the US one) and you might get to keep your student finance going as well. Obviously you'll have to factor visas, flights, insurance, living costs and accommodation (it'll be an expensive year) but it'll be a lot cheaper than going as an international.