Daniel Hamilton, director of the Center for trans-Atlantic Relations at the School of Advanced International Studies at Johns Hopkins, said Americans and Europeans tended these days to roll their eyes at each other and lament the paralysis of the other side. Dr. Hamilton, who has spent the past seven weeks in Europe, echoed other commentators in noting that the agreement to open talks on a far-reaching trade deal — one that would create a huge market operating on the same rules — represents the best way for Americans and Europeans to put their closeness on a new footing.

To judge from interviews with Berliners, though, there is little interest in or understanding of the complex trade talks, which are just starting. Rather, the data surveillance scandal has fired the popular imagination here, guaranteeing that Ms. Merkel, up for re-election in September, will raise the matter with Mr. Obama.

It is not as if Internet users outside the United States did not know that their digital movements might be watched, said Patrick Conley, 47, a media historian who lives in Berlin. “But you know it more exactly now,” he said. “In foreign policy terms, it is a catastrophe.”

That is particularly so in Germany, where state snooping was a dominant feature of the Nazi and Communist regimes. News that Facebook, which attracted 51 percent of German Internet users last year, according to the industry group Bitkom, had given up data to Washington’s surveillance program was a special shock here.

Mr. Conley was in the crowd for Mr. Obama in 2008. While he remembers the jubilation close to the speaker’s podium at the Victory Column, security forced him and his friends to sit in the surrounding park, far from the candidate, whom they watched on video screens.

The speech might have been electrifying close up, Mr. Conley said, but people near him drifted away before it finished. “We noticed that it was written not so much for Germans as for voters back home in Ohio,” he said.

Nonetheless, he and the same friends discussed going to hear Mr. Obama again on Wednesday, and were disappointed to discover that this time it was an invitation-only affair for about 5,000 people. “That is a shame,” Mr. Conley said.