I would let SOPA define it, but since their definitions are long and stuck in a PDF, I'll paraphrase from the source: http://judiciary.house.gov/hearings/pdf/HR%203261%20Managers...

   A site that either has a domain name registered outside 
   of the judicial district of the US, OR whose IP address 
   is located outside of the judicial district of the US.

So I think both of your examples could be within reach of SOPA. But then I think both youtube and facebook are out of reach of SOPA (instead they fall under existing law).