A year after Edward Snowden revealed the vast scope of the US data dragnet, America is still reeling from the fallout, which damaged ties abroad and triggered fears of "Big Brother" government.
In the latest twist since Snowden handed over thousands of US intelligence secrets in 2013, Germany has launched a criminal probe into snooping on Chancellor Angela Merkel's mobile phone.
The timing is embarrassing, just as US President Barack Obama is in Europe for Friday's events marking the 70th anniversary of D-Day, also being attended by Merkel.
Former CIA intelligence contractor Snowden, 30, remains on the run from US espionage charges, having been given temporary political asylum in Russia.
And on Wednesday, American whistleblowers urged him not to return home, warning he would not face a fair trial.
Ties between Washington and Europe, as well as other nations such as Brazil, have strained since the revelations, despite assurances from Obama that he is ending spy taps on friendly world leaders.
"In Europe, there has been a significant and negative change in both elite and public attitudes toward the United States over the past 12 months," said Heather Conley, director of the Europe Program at the Center for Strategic and International Studies (CSIS).
She pointed to a November poll that found only 35% of Germans believed the US government was trustworthy.
"In some way, Snowden prompted a global reaction to Iraq, to drone strikes, to Guantanamo," CSIS senior fellow James Lewis said at a Brookings Institution event in Washington.
The Obama administration has insisted the National Security Agency (NSA) needs tools to be able to thwart terror attacks not just against the United States, but also its allies.
"When you're operating in an intelligence enterprise, there's a whole lot that has to remain secret," said Robert Litt, general counsel to the director of national intelligence.
"But I think we could and should have found a way to explain more the legal authorities that we operate under to protect privacy and civil liberties."
Speaking at the Wilson Center think tank, he warned that growing reluctance by Internet firms to cooperate with state surveillance will lead to "intelligence failures in the future and people will wonder why the intelligence community was not able to protect us."
Ian Wallace, visiting fellow at Brookings, agreed that the NSA scandal "undermined the ability of the United States to work with its natural allies particularly in Europe."
Snowden "has emboldened authoritarian states that push back against the US model of multi-stakeholder governance" of the Internet, he said.
'All governments lie'
High-profile American whistleblowers launched the website ExposeFacts.org to encourage others to report on abuses of human rights and freedoms, or corporate wrongdoing.
"All governments lie and they like to work in the dark as far as the public is concerned in terms of their own decision-making, their planning," said whistleblower Daniel Ellsberg.
The former military analyst in 1971 revealed that the US administration had secretly enlarged the scale of the Vietnam War with bombings in Cambodia and Laos.
"When officials are assured that they will not be held accountable for their decision-making... even very intelligent men and women are capable of making crazy policies," Ellsberg added.
Other whistleblowers at the launch warned Snowden faces harsh consequences if he returns home to face charges brought under the 1917 Espionage Act.
"We've had enough examples to really understand that he will be rail-roaded, he will tried in a kangaroo court... and he will be imprisoned for the rest of his life," said Marsha Coleman-Adebayo, a former senior policy analyst for the Environmental Protection Agency who was sacked after reporting on malpractices by a US mining company in South Africa.
Snowden's lawyer confirmed that he is seeking to extend beyond August 1 his refugee status in Russia, granted after he was stuck in a Moscow airport when the State Department revoked his passport.
Snowden has voiced hopes of eventually settling in Brazil, but analysts believe it is highly unlikely the country will take him in, being keen to turn the page and rebuild ties with the US.