The Trump administration on Tuesday imposed visa bans on Breton, one of the architects of the EU's Digital Services Act, and other anti-disinformation campaigners who it says were involved in censoring US social media platforms.
The visa bans underline growing divergences between Washington and some European capitals over issues including free speech, defence, immigration, far-right politics, trade and the Russia-Ukraine war.
They come weeks after a US National Security Strategy document warned Europe faced "civilizational erasure" and must change course if it is to remain a reliable US ally.
The EU's act is meant to make the online environment safer, in part by compelling tech giants to do more to tackle illegal content, including hate speech and child sexual abuse material.
Washington has said the EU is pursuing "undue" restrictions on freedom of expression in its efforts to combat hateful speech, misinformation and disinformation, and that the act unfairly targets US tech giants and US citizens.
French Foreign Minister Jean-Noel Barrot said the Digital Services Act was approved in a democratic process and had "no extraterritorial reach and in no way affects the United States".
"France strongly condemns the visa restriction imposed by the United States on Thierry Breton, former minister and European Commissioner, and four other European figures," he wrote. "The peoples of Europe are free and sovereign and cannot let the rules governing their digital space be imposed by others upon them."
Breton, a former French finance minister and the European commissioner for the internal market from 2019 to 2024, was the most high-profile individual targeted.
"Is McCarthy's witch hunt back?" he wrote on X.
"As a reminder: 90% of the European Parliament - our democratically elected body - and all 27 Member States unanimously voted the DSA. To our American friends: Censorship isn't where you think it is."
Breton was replaced in the internal market role at the EU by another French politician, Stephane Sejourne, who is the EU Commission's executive vice president. Sejourne also criticised the US visa ban and defended the EU's Digital Services Act.
"No sanction will silence the sovereignty of the European peoples. Total solidarity with him and all the people of Europe affected by this," wrote Sejourne on X.
US Under Secretary for Public Diplomacy Sarah Rogers, when outlining the bans on Tuesday, described Breton as a "mastermind" of the Digital Services Act.
Earlier in December, Elon Musk's X platform was fined 120 million euros ($A210 million) by the EU for breaching online content rules.
The US visa bans also hit Imran Ahmed, the British CEO of the US-based Center for Countering Digital Hate; Anna-Lena von Hodenberg and Josephine Ballon of the German non-profit HateAid; and Clare Melford, co-founder of the Global Disinformation Index, Rogers said.
Germany's justice ministry said the two German activists had the government's "support and solidarity" and the visa bans on them were unacceptable, adding that HateAid supported people affected by unlawful digital hate speech.
"Anyone who describes this as censorship is misrepresenting our constitutional system," it said in a statement. "The rules by which we want to live in the digital space in Germany and in Europe are not decided in Washington."
Breton was not the first French person to be sanctioned by the Trump administration.
In August, Washington sanctioned French Judge Nicolas Yann Guillou, who sits on the International Criminal Court, for the tribunal's targeting of Israeli leaders and a past decision to investigate US officials.
