Exactly how would you define a "foreign site", especially when the countries of origin for the domain name and servers could be different? What about sites with servers in multiple countries?
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).