3.1 GPA, but 2 Ds and a F on transcript I am graduated in computational physics and from south asian country. i got  F and D- grades for elective physics courses in my first and second year. but i didn't retake those classes. another D+ grade for non major course. Will that grades keep me from going to a  grad school in USA ?
Maybe, maybe not. One can not say for sure. This depends on the particular programs you apply, on your luck and also the rest of your application (publications, recommendation letters and so on).

However, if I understand this correctly, you already received the bad grades. So if you want to study in the USA, just apply - you can (probably) not change anything anymore. You will see if they accept you or not and this matters more than the opinions of the people in this forum.

Welcome, by the way.