This website provides information about the AP U.S. History exam by CollegeBoard. It also has links to study skills and a practice exam.
The Gilder Lehrman website has nine short videos, one for each time period in the course.
John Greene’s YouTube channel, CrashCourse, has over 40 episodes to teach U.S. History. To see specific videos for each period, go to my website pages for each period. They are posted by period.