"We weren't prepared enough for the kind of coordinated misinformation operations that we are now aware of," Zuckerberg said, referring to Facebook's role in interference in the 2016 U.S. presidential election. "We've made these kinds of attacks much harder to do on Facebook."

Zuckerberg pointed to France's presidential election, the recent German elections, and Alabama's special election for senator as examples of recent elections where Facebook played a more positive role. The Facebook CEO noted that Facebook has gotten better at using artificial intelligence (AI) to flag posts that need to be removed.

But, he said, "We'll never be perfect on this. Our adversaries, especially on the election side, will have access to some of the same AI tools as we do. It's an arms race."

'We have a big problem here'
The European lawmakers, most of whom spoke in English, appeared extremely well prepared and to have closely watched the U.S. Congress's questions, and referenced them multiple times. They questioned the closed-nature of the Newsfeed algorithm, whether Facebook is a monopoly, and how it will comply with an upcoming new privacy regulation in Europe.