Block it where? SOPA, being a law from the United States is only valid in the USA. Different countries have different laws.
As an example, if China bans a site, is it banned in the USA? So if the USA blocks a site, is it blocked in the EU?
However it gets interesting with domain names. No-one really knows what would happen if the USA courts tried to delete a .ie domain. They wouldn't have the authority to do it. USA courts may have to result in ordering all ISPs to block that site, but people in other countries would still be able to do it. After all, the USA doesn't own the internet.
But, like I said, who owns .com? What could happen then?
SOPA does not 'delete' any domains. SOPA says that it can tell ISPs and Domain servers to not resolve certain domain names (within the US, the rest of the world doesn't, or shouldn't use US ISPs or domain servers). And it only affects domain names registered outside of the US. As others have stated here, the US already has existing measures to address US domains via ICE.
One of the reasons behind the claim: "SOPA will break the internet", is that many people in the US may start using non US domain servers to circumvent SOPA, and this would make our current routing and caching mechanisms inefficient.
I totally understand, but I encourage those that feel strongly about this subject to learn those kinds of details. There's a lot of Pro- and Anti-SOPA FUD out there.
As an example, if China bans a site, is it banned in the USA? So if the USA blocks a site, is it blocked in the EU?
However it gets interesting with domain names. No-one really knows what would happen if the USA courts tried to delete a .ie domain. They wouldn't have the authority to do it. USA courts may have to result in ordering all ISPs to block that site, but people in other countries would still be able to do it. After all, the USA doesn't own the internet.
But, like I said, who owns .com? What could happen then?