YouTube has a not so efficient Content ID system which helps copyright owners protect their copyrighted works and prevents other people from making money off it. But this system has been immensely criticised for its failure and its abuse by big corporations.
There have been so many reported incidents of big media companies abusing this system to make money off individual creators who were using footage by following all the rules. One such example of this is the b_viacom content-id which has been claiming videos of many people.
The ID b_viacom is one of the many Content IDs of Viacom which is an American mass media company now known as ViacomCBS and it owns the entire CBS television network and even popular TV channels like MTV, Nickelodeon, BET networks, Comedy Central and many others.
So if your video contains any footage from any shows or media which ViacomCBS owns then your video will get copyright claimed by them and the video might also be banned from viewing in many countries. If you think you have followed the rules, then you can dispute the claim or you might like to learn about how ContentID works.
But if you are a viewer and you are noticing the error message on a video you want to watch ‘the video has been blocked in your country due to a copyright claim from b_viacom’, then first use this tool to determine the countries where the video has been blocked and then use a VPN to connect to one of the countries where the video is not blocked and you should be able to watch the video.