This text has been found in violation of H.R 3261, S.O.P.A and has been removed.
S.O.P.A stands for Stop Online Piracy Act. It was a bill introduced in October of 2011 to prevent piracy, copyright infringement, and the trafficking of counterfeit goods online. S.O.P.A was very controversial, as many accused it of limiting free speech.

I don’t know why you would need to know about this, but you can find it in a high-ranked definition of America, so hey, context!
Someone: Hey, what’s this “ This text has been found in violation of H.R 3261, S.O.P.A and has been removed. ” on the definition of America mean?
Nerd: It’s a bill passed to prevent illegal activity online.

Someone: You’re a nerd, stfu.