Jumping in with some suggestions here. First, your research experience gives you a lot of power on choosing schools (even if you "got nothing to show for it"
), and even without a "4.0" GPA you can get accepted to quite a number of great programs. Schools don't just look on one aspect but a combination of all three "main" ones -- your scores (GPA and GRE/pGRE), your research, and your statement and recommendation letters.
That said, different universities tend to require different parts of those. You can compare the requirements online.
University of Washington for instance, has a minimum GPA of 3.0. University of Colorado, Boulder is the same with GPA, but specifies the average GRE/pGRE scores of the students that were accepted last year.
As for considering different programs, you can go over the offered research specialties and programs of schools in the USA, it might help you decide which program is suitable for you, the explanations are very thorough, and you can use the search engine to look for schools with certain academic conditions (research budget, faculty/student ratio, etc).
* Note: The information on gradschoolshopper.com comes directly from the department contact people and is updated yearly.
I hope this information helps. Good luck in your graduate studies!
American Institute of Physics