WASHINGTON—A Facebook executive said Sunday that the company would introduce new measures on its apps to prompt teens away from harmful content, as lawmakers scrutinize how Facebook and subsidiaries like Instagram affect young people’s mental health. Nick Clegg, Facebook’s vice president of global affairs, also expressed openness to the idea of letting regulators have access to Facebook algorithms that are used to amplify content. But Clegg said he could not answer the question whether its algorithms amplified the voices of people who had breached the U.S. Capitol on Jan. 6. The algorithms “should be held to account, if necessary, by regulation so that people can match what our systems say they’re supposed to do from what actually happens,” Clegg told CNN’s “State of the Union.” He spoke days after former Facebook employee and whistleblower Frances Haugen testified on Capitol Hill about how the company entices users to keep scrolling, harming …