Europe's worst fears before the Putin-Trump meeting - that Trump would recognise Crimea as Russian or cancel US involvement in military exercises on the continent - did not come to pass. But as Air Force One returned to Washington, European leaders said that US standing in the world had been broadly damaged.
"The danger from the point of view of European security is that there is a risk that he is sending a message of non-interest in those issues," said Carl Bildt, a former Swedish prime minister. "At the extreme end, it could be seen as a tacit acceptance of what Russia is doing."
The Trump-Putin meeting was a dramatic contrast to the last time US and Russian presidents sat together in Helsinki, in 1997, when Bill Clinton met Boris Yeltsin as Washington worked to push forward with Nato expansion over Russian objections.
Back then, Clinton acted not only as the US leader but as the leader of the free world. This time around, Trump declared the European Union a "foe" on trade but called Putin "a good competitor."
"Trump is sitting now with Putin as the president, the national president of the United States and America first, not as the leader of the West and of the free world. By choice," said Stefano Stefanini, a former Italian ambassador to Nato who is a security consultant in Brussels.
"Since the Iron Curtain, the US has stood up to defend Europe from an aggressive Russia," said Stefanini. "If Trump comes to the conclusion that he can deal with Russia, irrespective of what Russia does in Europe, that's a 180-degree reversal of the relationship."
A lot has changed since the 1997 summit.
Javier Solana, who was Nato Secretary-General at the time, was recently denied an electronic visa waiver for travel to the United States because he had visited Iran five years ago. Hungary - which diplomats say was the first Eastern Bloc nation to bang on the doors of Nato and demand membership - is now led by Prime Minister Viktor Orban, who in a meeting with Putin condemned sanctions against Russia and declared that "we support the normalisation of relations between Russia and the West."
Some diplomats said that although Trump and Putin did not appear to have made any grand bargains on Ukraine or Nato that would directly hurt European security interests, relations between Europe and the United States had worsened in the past week.
"The US looked weak, and that could embolden Putin," said one "depressed and concerned" senior Nato diplomat.
Ukrainian President Petro Poroshenko also appeared to chafe at Trump's lackluster defence of his country, writing defiantly on Twitter that "we are ready to defend our land even if we remain all alone, without international support."
Even before the meeting broke up, some European leaders were saying that they needed to rethink relations with the US.
"We have to re-evaluate the partnership with the US. We can only do that in a confident and sovereign Europe," German Foreign Minister Heiko Maas said. Trump repeatedly ripped into Germanyin the past week over what he called its lagging defence spending and the unfairness of its building Nord Stream 2, a natural gas pipeline across the Baltic Sea that Eastern European nations have complained will make their energy supplies less secure.
Some Eastern European politicians said Trump's willingness to give Putin the benefit of the doubt made them feel less secure.
"And now, as a US ally, we are supposed to believe that if President Putin launches a hybrid war, or even a nuclear strike against Poland, President @realDonaldTrump will threaten to nuke him back," Radoslaw Sikorski, a former Polish Foreign Minister, wrote on Twitter.
But some leaders and analysts said they were relieved that a true reordering of European security did not result from the Trump-Putin meeting.
"All the negative expectations that the two presidents could agree on something that would hurt the allies of the United States, it did not happen," said Norbert Röttgen, leader of the foreign affairs committee in the lower house of the German Parliament. "The absence of the negative is something positive for us."
The absence of any substantive announcements by Trump or Putin may be a sign of a broader stagnation in the bilateral relationship, with Trump boxed in by tough-on-Russia hardliners in Washington, one analyst said.
"There's a disillusionment on the Russian side," said Tomas Valasek, a former Slovak ambassador to Nato who is the head of Carnegie Europe, a think-tank.
"The idea of a grand bargain presumes that Putin has things that he wants from the West and that he trusts Trump to deliver," Valasek said. "There's so little trust."
