Most people don't realize that "fair use" is just something that gets thrown around the YT circles. If I own the audio or visual content and you use 1 second of it, I can take down your whole video.
The usual process is the following: you upload a video, it gets hit by ContentID, you decide to file a dispute, the dispute goes to the owner of the material, they have 30 days to decide yay or nay. If they say "nay this is mine and I'm not giving it to you", it's game over. You can cite fair use, but unless you are willing to take them to court, there is nothing you can do about it. You cannot complain to YT, they are intentionally keeping their distance.
So often you can see people using a little boiler plate snippet of fair use in their description thinking this is perfectly fine. The reality is that the owners of the materials are usually big corporations that a) don't read video descriptions and b) don't really care of what YOU think is fair use.
Unless you have the resources to take someone to court or are backed up by a MCN that is willing to do it, fair use is pretty much pointless. If you are using someone else's material, they can take down your videos with a click.