Bad GPA Because I Went to a Competitive High School?

I'm a Brazilian student applying to US colleges.

All was fine with my SAT/TOEFL grades and my extracurriculars which are pretty good but since I've studied all my life in a top school here, my gpa is not good, i'd say a 2,8.

Is this going to affect a lot in my application considering my 1500 SAT grade, my 110 TOEFL and my excellent extracurriculars?

What's the actual importance of the GPA in brazilian/international students? DO universities know the difference between a 4.0 GPA in Brazil and a 4.0 GPA in USA?

College will understand that your GPA is due to your competitive school if you have an excellent SAT score, as well as SAT subject scores.

When the College lets you submit extra info, you may want to submit proof of how competitive your school is. For example, your rank in the school might be better than the GPA. Or if your high school sends 20% of people to "top universitites" you can show this off as well. Getting a teacher to write a recommendation about how competitive the school is also works