As reported by the Google Earth Blog, there is now a new layer in Google Earth for geotagged YouTube videos. In the Windows version of GE the videos appear right in the description bubbles; in the Mac and Linux versions you get a link to view the video in a browser.
It works like most other layers – as you zoom further in, more videos appear. To get your video to appear, simply allow embedding and map its location. It should then appear in the next layer update, which occurs roughly once a month.