I can assure you that at Cornell, as long as you are making satisfactory progress towards your degree, you will be supported. I'd be willing to bet a large amount of my own money that this is also true at any other major name-brand US program. You can't be a successful student if you don't have money to live on, and Universities have a very large interest in you being successful. The nine month thing is just a formality. You'll be able to sign up to TA over the summer or you can find an RA. It may not be your dream RA, but there are professors with more money than students who will happily pay you.