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.
Even if you are only sending in copies digitally, it is a good idea to print your resume (as it’s possible that hiring managers may be doing so) to be sure it prints on a single page, and is easy to read in printed form. Reading over a printed copy of your resume will also help you ensure that there is plenty of white space on the page and it looks professional.