Officials from various states such as Ohio, Pennsylvania and Texas are already trying to acquire election systems.
The Facebook CEO says he is "open" to testifying in court if he's the "right" person, and that the company had made "major mistakes."
A British political consulting firm is reported to have harvested without permission personal information from more than 50 million Facebook profiles.
Social media giants are facing questions on paid content sponsored allegedly by Russia during the U.S. Presidential elections.