If you studying in the USA, you are going to have some form of medical insurance... As the EU10 (the green medical) card doesn't cover any medical treatment outside of the EU, and we haven't got any arrangements for the government to cover any medical bills in America...
Due to import/export regulations you won't be able to get anybody to post your medical supplies to you in the states, and you really wouldn't want to take the risk of insulin being transported across the world in dubious uncontrolled environments that's for sure...
You can arrange to take so much supplies with you, but you will have to check with the airline you'll travelling with concerning keeping the insulin in the cabin with you and not the haul of the plane... And if you are travelling back to the uk regularly you can pick up more supplies while home to take back.. But you will be limited to what the doctor will prescribe for you.. This would however limit some of the costs for you..
But as noblehead said, contact the DUK, as they will give you full information concerning what you can and can not do, and also point you in the direction of medical insurance cover to fit your needs