It’s awesome that you have such an intense dream and you should pursue it. Remember that your energy goes to what you think about and “What you think, you become.” So directing your thoughts to this goal will show up many new ideas on your way to help you get to your goal and live your dream.
Many universities in the US have scholarships which help you finance your studies – but you must be VERY good at something :)

Maybe you have also heard about student exchange programs – which you do before you’re 18 :) so maybe you’re mom might help a little too. It’s basically an exchange of an American student and a foreign student for a year or semester in high school.

You can do some research on these things. Setting yourself a goal and figuring out the little steps to get to it is already half of your success. Now believe in yourself and follow your dream.