Amazon's Twitch service (and by extension also AWS's Interactive Video Service product that uses all the same backend stuff). Their video player is either fully a WASM thing or has some WASM components, I'm not completely sure which.
See, that's the problem. As long as WASM is not able to pull its own weight and needs JavaScript to provide the spine it will languish in a niche or two. Ultimately someone will decide that supporting two different languages and ecosystems is too expensive and not worth the marginal advantage and it will go back to JavaScript only.
We've been there and we have done that with Java applets.
Those libraries are not something will be able to be JS only anytime soon, and no, Java applets has never allowed us to use C/C++ libraries on the web before.