In the United States, a CV is almost exclusively limited to professions in academia, science and medicine. In the case of academia, the main focus of the CV should be to identify yourself as a scholar. The added length, should be filled with proof of your skills as a teacher, scholar, and your knowledge of education. A CV should be thought of as a living document, and it will change frequently based on the updates in your education and career.
GPA. As mentioned above, your GPA is only necessary if you are a recent college graduate and do not have work experience to back you up. There are a few jobs that require a GPA, however, including engineering and finance.