Backlinks to videos

How big of a role do back links play in the youtube algorithm?

As for ranking videos on Youtube itself, that’s a whole other beast, and while I think backlinks have some bearing on the equation, the larger signals are definitely driven by a different algo that looks at user engagement metrics.
Absolutely. A video, whether it is hosted on YouTube, Vimeo, DailyMotion, or any other site, is still a webpage first. At the end of the day, Google evaluates the page - and that includes on-page factors, social media mentions, backlinks, and more.
If you’re up to snuff on your SEO knowledge, you can certainly rank a YouTube video with backlinks. With YouTube being a high-authority site, there are times when a video will rank with minimal or no backlinks.
Along with backlinks, you should also look for video embeds. Video embeds often provide better results than straight backlinks, but it’s a good idea to mix it up with embeds and backlinks when possible