From what I could tell the only problem with the SOPA was if USA had something to do with it, no matter how tiny, such as having just one server in the US would allow them to get to you.I'm no expert but i believe they can go after us outside the USA.
Let's say i download some content of a band with a contract with an american company. I'm committing a "crime".
Now, my country can allow the feds to come here and bust me or not...
I think that's where the difference lies.