On Facebook, adding your YouTube handle does not work, as Facebook will remove the @ (at) symbol. YouTube links without the @ symbol only works if you have custom URL.

To make YouTube handles work on Facebook, you need to add the + (plus) sign on it¹, so instead of @AnimMouse, it should be +@AnimMouse.

This will prevent Facebook from removing the @ sign and allows your Facebook viewers to click the link to view your YouTube channel.