The House's Stop Online Piracy Act (SOPA) and the Senate's Protect Intellectual Property Act (PIPA) have raised concerns among technology firms as they could see websites shut down for allegedly encouraging piracy.
Technology companies such as eBay, Facebook, Google, Twitter and Mozilla have all voiced their opposition to the two bills.
"Like many businesses, entrepreneurs and Web users, we oppose these bills because there are smart, targeted ways to shut down foreign rogue websites without asking American companies to censor the Internet," said a Google spokeswoman cited by Reuters.
On Wednesday, Wikipedia temporarily shut down its website in protest against the two bills but failed to enlist other companies in its campaign for a 24-hour internet blackout.
EU warning about open internet
In Europe, policymakers have grown increasingly worried about the draft legislation.
Ryan Heath, spokesperson for the EU's digital agenda commissioner Neelie Kroes, told EurActiv that the EU executive was closely monitoring the developments in the US.
"Today's protest clearly shows that digital issues are now mainstream political issues," Heath said.
"While we acknowledge the importance of combating illegal content online, the means to achieve this objective must be effective, proportionate and preserve the advantages of an open Internet. We expect the extra-territorial impacts of any US legislation would be minimised."
Marietje Schaake, a Dutch liberal member of the European Parliament who was recently appointed to draw up a report on internet freedom globally, has led a campaign to get the bills amended.
In December, she wrote a letter to the US congress saying SOPA and PIPA "will be detrimental [to the] internet as a driver of economic growth and for fundamental right, not only in the EU, but globally."
The two draft bills, she said, would allow blocking entire websites for infringing copyright or facilitating the infringement of copyright, a notion which can be interpreted very broadly.
"I am concerned about that because it is a disproportionate and draconian measure," Schaake told EurActiv. "This is probably the reason why so many tech companies and big organisations like Wikipedia are concerned because it attacks the heart and the core infrastructure of the internet which is global."
If adopted in their current forms, the two bills would bring US legislators on "a slippery slope" where other types of websites could also be shut down.
"We were very much afraid of a slippery slope, a mission creep," Schaake said. "Now we're talking about copyright but who knows there may be people who believe certain content is offensive and would lobby for blocking those as well. And then you have a slippery slope which actually is quite dangerous."
The legislation has been a major priority for entertainment companies, publishers, pharmaceutical firms and many industry groups. They maintain the proposed legislation is critical to curbing online piracy they say costs them billions in revenue each year.
The Recording Industry Association of America (RIAA) derided the internet blackout of Wikipedia, describing it as a gimmick. “It’s time for the stunts to end and those who claim to care about rogue website theft to back up their rhetoric and work with us on meaningful solutions,” the RIAA said.
But Schaake said there were other ways for artists to get financial rewards for their works, citing web-based startups that are offering streamed music online in exchange for advertising space.
"As a liberal I believe that there should be free competition and that we should not be in the business of disproportionately protecting one business model over others," Schaake said.