Thank you, Cup o' Joe. Your reply was remarkably informative and amazing!
On one hand, I did want to make preparations for some worse case scenarios and tried to apply for some graduate school when I was not fully prepared before reading your reply . On the other hand, visa may not so easy to get in some cases , even if you have got a funding. That should depend on your nationality, educational background (students who were majored in nuclear, weapons, aviation, and some other majors related with national defense and security may have some troubles in getting their visas ), intended major and college in the U.S., and surely your performance in visa interview (in my country), and many of my friends, who were in the same major with me, had been rejected before. Therefore, I created this topic for helps, and your explicit answers had made the risks and consequences clear to me.
Thanks again !