The unspoken question: is the world on the verge of an historic power pivot -- one pushed by President Trump that re-shapes world order, diminishes the EU, and enables others like Russia?
In Malta, she is already an outsider, invited to some meetings, but not all. She won't join the 27 other EU leaders when they discuss the comments made by Donald Tusk, President of the European Council, about Trump: that the new US President is a "threat" to European order.
So far Trump has backed Brexit, been ambivalent at best about the EU and accused Germany of using the EU to steal American business.
The British Prime Minister hitched her political wagon to Donald Trump's fortunes a week ago. Kudos back home was rapidly replaced with rancor, as the Trump administration's so-called "Muslim ban" was revealed hours later.
Most European leaders are repulsed by Trump's decree suspending all refugee admission for 120 days, and his travel ban on anyone from seven named Muslim-majority countries. But this barely scratches the surface of their deeper fears.
That Trump took this decision in semi-secrecy without any apparent input from key senior staff from the State, Defense, Homeland Security and Justice departments is a bad sign of what's to come.
Trump's "America First" rhetoric -- branded by an aggressive fast track to unilateralism -- threatens a rapid reshaping of global diplomacy: witness National Security Adviser Michael Flynn's throwing down a red line against Iran and Trump's tweet, declaring that Iran had been put "on notice".
Secrecy and spats
Running past the reflecting pool in Washington DC's iconic National Mall last week, I was struck by its murky green waters. The winter clouds had robbed it of its reassuring serenity, but it was the absence of its clarity that I found most unsettling.
Only a few weeks earlier, these waters had provided the backdrop to history unfolding, as they do every four years during the reassuring spectacle of the peaceful transition of power. Yet this time, the words that fell on upon its surface were darker: President Trump heralding his vision of "America First".
What is currently unsettling European capitals and others around the world is Trump's style. Not just the Twitter spat with Mexico's President, not just his apparently brusque style with Australia's Prime Minister Malcolm Turnbull
, but his unconventional secrecy.
In rolling out his apparently haphazard and ill-conceived travel ban, Trump has put a match to an accumulation of tinder-dry worries, grown in the run up to his presidency. What he has done is the diplomatic equivalent of setting the school on fire while bunking off to smoke behind the bike shed.
Setting aside the obvious problems with Trump's travel ban -- that Americans are statistically more likely to be killed by a child with an automatic weapon or falling out of bed than by a refugee, that it flies in the face of all the successful counter-terrorism tactics honed by US and its allies in recent decades -- it is the insidious nature of the decision making and crafting of the decree that is troubling America's traditional allies.
Trump's team was smart enough to get him elected and is smart enough to have gamed out some of the repercussions.
Fanning the flames
So why create so much turmoil and uncertainty?
Is Trump's inner politburo, the one often surrounding him as he launches his decrees, afraid that their project will be stopped? Are they afraid that its flaws will be found out? Or is it that they do have a grand plan, privy only to the most-trusted members of the President's inner circle?
The old adage of no smoke without a fire raises fears as to what other secrets is Trump keeping, and what his core trusted advisers are planning.
In Malta, the members of the EU Council fear that the Muslim-oriented travel ban will fan flames already licking the central plank of the European project: open borders.
Unlike in the US, the danger of ISIS exploiting the refugee ban to gain entry to the continent is a major security concern. His policy enables populist nationalists like UKIP's Nigel Farage, France's Marine Le Pen, Holland's Geert Wilders and Germany's AfD, who all want to bring the EU down.
The reality for them is now very clear: Trumps apparent ambivalence to EU is a chimera for his hostility toward it.
So what happens behind the White House bike shed next is a worry.
A secretive plan to embrace Putin above the heads and advice of most European leaders would not just add further distance between Brussels and Washington, but ignite another smoldering ember of European contention: sanctions over Ukraine.
Some of Putin's European allies have been calling for an end to this policy, as it hurts them too. Putin himself is only too happy to see America's historic European allies squabble and weaken.
If it comes -- and the Kremlin's fulsome and all but effusive read out of Putin phone conversation with Trump
indicates that it could -- it will become a matter of urgency for EU leaders to put differences behind them.
If this were Trump's next move, Tusk could be forgiven for thinking Europe does indeed face an existential threat. Europe's experience would become a fast-learned object lesson for other capitals around the world.
America First is more than a battle of ideals; it is a vision of a new world order that places the US dollar ahead of all else.
Only Trump's inner circle currently knows how far he is willing to go to achieve this.