As the nation marks the 20th anniversary of Sept. 11, the legacy of the terror attacks and their aftermath continues to unfold, from insurrection at the U.S. Capitol to the resurgence of the Taliban in Afghanistan.

Veteran FRONTLINE filmmaker Michael Kirk and his team have been chronicling 9/11 and its impact for two decades in multiple FRONTLINE films, including America After 9/11, an epic re-examination of the decisions that changed the world and transformed the U.S. across four presidencies. The two-hour documentary is now streaming on FRONTLINE’s website, the PBS Video app and YouTube.

Kirk joins The FRONTLINE Dispatch to talk about the through line from Sept. 11 to Jan. 6, as well as ongoing challenges for the U.S. president, the country and the world. "By pulling back, we discovered a lot of dots that could be connected, that actually had a strong relevance to today," Kirk says in the episode.