Unless these are identified as public domain, you have to check the licensing info for each site.
Beyond Wikipedia: Background & Reference Sources, from the Mina Rees Library at the Graduate Center, has many more archival sources.
The Public Domain Project by POND5 Download thousands of historic media files for your creative projects. Completely free & made available by Pond5.
The Public Domain Review images, books, audio and film in the public domain
AP Historical Archives on YouTube “Film and video archive of AP, the world’s largest and oldest news agency. Archive has over 1.7 million news, sports, entertainment and fashion stories dating back to 1895. They also have a British Movietone channel – https://www.youtube.com/c/BritishMovietone”
American Archive of Public Broadcasting 40,000 hours of video and audio, thousands of high-quality programs that have had a national impact, from the Library of Congress and WGBH.
British Pathe Newsreels, video, archive, film, footage, and stills going back a century.
Vanderbilt Television News Archives (via NYPL) Search and view video segments of CNN (1980-present) and NBC (1968- present) news archives. It will ask you to register if you want to view clips. Other major news networks are searchable but not streaming, and for those, a DVD can be requested for a fee.
Internet Archive’s TV News Archive The collection dates from 2009 to the present and contains news programs from national U.S. networks and stations in San Francisco and Washington D.C. New content will be added 24 hours after the programs have aired. You can search the broadcasts’ closed caption transcripts by keyword.
C-SPAN Video Library (1987 – Current) Searchable database of all of C-Span programming, search for clips by topic, keyword, person etc. Here’s a list of what you are free to use on C-Span.
UN Multimedia Audiovisual Archive 70 years of UN news, meetings, documentaries, including B-roll and raw footage.
The Open Video Project A shared digital video collection, for research and educational purposes.
Internet Archive Moving Image Archive Thousands of digital movies, many for free download.
Footage.net ($) “The Stock, Archival and News Footage Search Engine”