Grades or GPA are just one component of application process. They only show one aspect of the applicant. However when you apply for "Graduate Program" (Masters and PhD) in USA, often universities look at the overall profile and inclination of candidates towards a perticular area and/subject. Unfortunately only GPA alone doesnt reflect the overall picture. Universities, hence rely on other components, one of which is "Statement of Purpose" (SoP). A well drafted SoP can make or break your chances of admission, especially in top tier universities.
With the experience that I have gained since 2010, I have seen many cases where an average looking profiles got into top schools in USA, just because the students were able to put their thougths effectively and convincingly in the form of SoP.
 
Note: As the title says, its an SoP review. I will help you and guide you write a first draft of SoP and later I will review it and make some tweeks in it. You are expected to work on it as well. I dont provide a generic SoP to all the students. Each student is uniques, so should SoP be.