Ouch-very low for any US college. You would need to find out from your HS how your grades translate to the US system. I doubt you are accurate in your guess, even for unweighted grades (which are used by UW).
In the US HS grades usually mean a C (2.0) is the average grade including those who do not go past a HS diploma of any kind. Most college applicants will have a mix of A’s (4) and B’s (3), perhpas some C’s, regardless of the caliber of four year college applied to.
Since you obviously were admitted to a US college and have good grades there your foreign HS record is likely not a problem for admissions. Focus on your college gpa.