I think you're worrying a bit to much. My sister and I are nationals from Nicaragua, but I came to the United States before high school. My sister stayed. She did her undergraduate at a national university, and now is doing a Masters at USC. By no means is any undergraduate university in our home country even close to the reputations of UT, but she managed. As far I can tell, her GPA was around 3.86, GRE subject around 820 and i'm not sure about her general.
Thanks, I do think I am worrying a lot, it's just that I'm really anxious about one of the professors who are writing me a reference letter: I asked him when he was in a bad mood and he sort of took some questions I asked him the wrong way. Are you two U.S. permanent residents? If you are, then you aren't considered international students since you are eligible for U.S. gov't grants.
I recently realized something that might complicate my application: my school converts percentages to GPA differently from most schools. Here, if your average mark in your course is 85% or above, you get a 4.0 (an A). 80% and above is 3.7 (A-), 77%+ is 3.3 (B+), 74%+ is 3.0 (B), etc. But I think at most schools you need 90% and above to get 4.0, and 85% is only a B. So does that mean that schools will view my 3.25 GPA as a 2.25 GPA (!!!)? Keep in mind that my school marks hard and that the class average in physics is a 2.46 GPA (~ 69% in percentage based on average marks in a course)