I wouldn't exaggerate like that. In the event that SOPA passes and is used in all the ways that we fear it will be, the solution for those of us in Europe is quite straightforward: we just carry out - it just means we're going to be concentrating on European specific stuff rather than catering to European/American concerns.
Put it this way, if it were to happen, I could fully envisage Wikipedia starting up a European based server (if they don't have one already) in the .eu or similar domain, where the US has no real jurisdiction.
That's the beauty of the internet: it's fully designed to reroute around blockages. What will happen is that the US will be considered a separate internet to the rest of us, and the consequences of that are still beyond thinkable, but not insurmountable.
Also, the other question: if this is a best hope for the parties trying to push it through, what's their fallback position?