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.
If you have major gaps in employment, there are a few ways to make them less noticeable like a change of resume foramt. It is important to be honest about gaps in your resume and not try to cover them up, but to also make them seem productive and intentional. Adding volunteer work or classes in the time you were unemployed is highly valuable and fairly simple to get starter with.