Praise be to Allah.
You have done well, may Allaah bless you, when you followed the laws of Allaah and put on hijaab. You should note that there is no obedience to any created being if it involves disobedience to Allaah. You have to continue to wear hijaab and follow all the other laws of sharee’ah. But we are afraid that if you go to America to study, you will face waves of fitnah from all directions, all kinds of doubts and forbidden desires. If you can study in a university or college which pays attention to the rules of sharee’ah such as wearing hijaab and avoiding mixing, then that is what you should do. May Allaah help us and you to do all that is good.