The two have long been divided on whether speech can be restricted, and when. Under the Trump administration, the gap is widening.
The potential for major penalties in the European Union could test the boundaries of online speech and inflame tensions between the U.S. and Europe.
China vowed countermeasures and the E.U. promised a unified response, while Britain and Japan refrained from immediate retaliation.
European leaders have said they would prefer to negotiate. If that fails, their response could go beyond anything they’ve tried before.