As a US citizen, I didn't want to be the one to say this (in response to e.g. https://twitter.com/#!/foxhuntingx/statuses/1589645062094274... ) because it might sound arrogant, but seriously, Herr Duerksen is correct: People in Australia, UK, and other non-US places affected by the en.wikipedia blackout can cover their eyes and ears and pretend SOPA doesn't affect them but I think this is a ridiculous stance.
Yes, much of the world looks to/points at the US for various speech &c. policies. Furthermore, much of the Anglophone world uses US internet services and products that would likely be affected by SOPA (facebook, youtube, reddit, en.wikipedia, 4chan, etc.). If it passes, SOPA probably will affect you whether you live in Boston or Brisbane.
There are many people who seem to hard time grasping the fact that US law applies to US sites, regardless of what country you are in (see: "Google turned off my 10 year old's Gmail even tho I live in the UK and it's a US law!!! US law doesn't govern me!!" <- yes but US does govern Google, which operates out of the US).
This fact is a good argument for creating competing services not based in the US (even tho it'd probably be illegal for us 'murkins to use them :/ ).