"How exactly does this affect "billions" of people?
Last time I checked, Youtube was not available in many countries outside the U.S. Also, correct me if I'm wrong, but U.S. law is "U.S." law, not "World Law". Court decisions, landmark or otherwise, made in the United States don't affect law in other countries, especially since most of the world uses civil law as opposed to the U.S. which uses common law."
Wow....since you are obviously too stupid to figure it our for yourself, I'll spell it out for you.
Youtube is available in most countries. In fact so many countries, that billions of people have access to it.
http

/mashable.com/2007/05/30/youtube-bans/
Also, when youtube is forced to take down one video by an american company (citing american law), then nobody can watch this video. Even those outside of america. So yes, american law can affect the rest of the world.