The "sincere" (their word) letter of congratulations to Donald Trump penned this morning by the big cheeses from the European Commission and the European Council oozes EU angst from every line.
Messrs Juncker and Tusk rushed to remind the US president-elect of "shared values of freedom, human rights, democracy and a belief in the market economy" in a way that lays bare their very clear fear that Mr Trump doesn't prioritise these values at all.
Donald Trump's much-touted boast that he would deliver "Brexit plus plus plus" on election day rings shrilly true in the ears of Europe's political elite this morning.
Britain was much appreciated in EU circles, yes, but it was also always regarded as a reluctant European, a rule-breaker, an outsider.
But the deafeningly angry roar of millions of anti-establishment, nationalist-minded US citizens suddenly makes the prospect of a French President Marine Le Pen, an Italian premier Beppe Grillo and a Dutch Prime Minister Geert Wilders that much more plausible.
The politically correct congratulations trickling their way to Donald Trump's in-tray today were sent through gritted teeth by leaders across Europe, worrying about the populist backlash in their own backyard.
Key EU nations France, Germany and the Netherlands are steaming towards elections next year with increasing numbers of voters biting at the bit to give what they believe to be a self-serving elite - and their attack dogs: market capitalism, multiculturalism and globalisation - a good kicking.
Italy's prime minister risks losing his job in a matter of weeks, depending on the results of a referendum he called on changing the Italian constitution.
In what is possibly the political understatement of the morning, Matteo Renzi mused after Donald Trump's declaration of victory that "we are in a new (political) season".
By far and away the most effusive European reaction to the US elections came from the jubilant leaders of populist anti-establishment parties from Budapest, to Berlin, Vienna and beyond.
But the right-wing nationalists already in government in Poland didn't find time to gloat.
Their key concern following the US election is the impact on global security, rather than politics.
Poland, the Baltic states and, of course, Ukraine worry first and foremost about President Vladimir Putin and what they perceive as an increasingly aggressive Russia.
In the wake of Russian actions in Ukraine - but also cross-border terror attacks by Islamist extremists and irregular migration across the Mediterranean - Europe as a whole has turned increasingly to Nato for help and reassurance.
Yet a few weeks ago, The Atlantic publication summed up its reading of Donald Trump's attitude to the transatlantic body in the dismissive "Nato Shmato" headline - despite Nato having served "as the cornerstone of global security" since World War Two.
Mr Trump certainly made waves during his election campaign when he indicated that US military support for Nato member states could be conditional on whether countries meet their financial obligations to the bloc.
If he keeps his word, only four of Nato's 28 members would qualify for support from Washington in the case of a war.
Donald Trump's rhetoric - inexplicable and abhorrent to some, refreshing seductive and honest-sounding to others - propelled him to election victory on the anniversary of the fall of the Berlin Wall, a moment that changed the course of European history.
On Wednesday former Italian Prime Minister Enrico Letta, a man rarely associated with hyperbole, described the US vote as the biggest political rupture since then.
He and other notable European figures insist Mr Trump's victory is a wake-up call for Europe.
Across the continent, people are certainly sitting up and taking note, but the lessons they draw from the US election are shockingly different, depending on their background, their politics and their fortunes in life.
From the European perspective, Donald Trump's victory can be seen as the second act in a ground-breaking play that opened with Brexit and a widespread, cross-continental sense of popular betrayal following the 2008 economic crisis.
It's proving to be a wildly unpredictable drama - with an agitated audience dictating new script lines.