I am a student who is hoping to start a YouTube channel which focuses on history in the last 100 years -I have had a very difficult time finding free to use video (My first project is about WW2) -I have looked at archives like Pathe, Reuters (Screenocean), but all of the clips they have for sale are really expensive (250$) -I was hoping some historians out there might have some tips on archives/sites which have free to use clips from the time period.
The Internet Archive is often a much better place to be searching.
Rather than the Library of Congress, you probably want to be looking through the National Archives instead. This way you can be more sure about the copyright status of what you are taking as source material.