Not just the important relationship between the two countries, but, potentially, the future of the European Union.
Trump's chaotic entry to the global stage is already having repercussions. Trump's actions could trigger another tumultuous year in a fragile Europe ever more fragmented by nationalism
In some countries -- such as France and the Netherlands -- the populists could win. Victory for these parties could pull the EU further apart, already weakened with the crisis triggered by Britain's Brexit vote.
Europe is in a fragile place right now, a situation exacerbated by Trump's apparent ambivalence to its future and easy readiness to criticize leaders like Merkel.
As both President-elect and President, Trump has at times spoken with the diplomatic dexterity of a rhinoceros. In the case of Merkel, he has lambasted her handling of Europe's refugee crisis, calling it a "catastrophic mistake." When asked who he would trust, Merkel or Putin, he said: "I'd start off trusting both."
Trump, who is fixated on trade imbalances, has not just focused his attacks on Merkel, but has also accused Germany of a massive imbalance and taking business from the United States.
Add to that already combustible mix a speech by Trump's VP Mike Pence in front of Merkel in Germany recently, where he tried to reassure Europeans about Trump's support without once mentioning the EU
, and it is clear just how critical to Europe's future next week's White House meeting could be.
With key elections taking place this year, one thing seems certain: Whatever the outcome, the status quo in Europe cannot continue.
History has a habit of repeating itself in Europe. But in the relentless world of 24-hour news, this is easily overlooked.
What we are witnessing on both sides of the Atlantic is a steady slip toward division and change for the sake of change.
But for all the talk around Trump's presidency, it is in Europe where this decade's most profound political changes could occur.
Elections in the Netherlands on Wednesday and in France next month risk dismantling a world order that has seen peace in Europe for nearly three generations.
In Holland, Geert Wilders and his Freedom party
are surfing a wave of anti-immigrant sentiment, buoyed by dissatisfaction with traditional political parties.
In France, the National Front's Marine Le Pen -- who inherited the mantle of nationalist leader from her father -- is doing what he never managed: taking his fringe right-wing party and turning it into potentially the most popular political force in France.
And when Germany goes to the polls later this year, Europe's former moral compass, Chancellor Merkel, faces increasing dissatisfaction with her handling of Europe's refugee crisis, making her vulnerable to attacks from the right.
The depth to which they are cutting in to her political real estate could be measured at her recent speech in front of Pence and Europe's upper-echelon diplomats
. She said: "Islamist terrorism is also being perpetrated very close to the European Union's external borders and thus has a strong impact on Europe. This is another reason why cooperation with the United States of America is of course very important for us."
For the leader who garnered global praise for telling Syria's war ravaged refugees Germany's doors are open to them, her comments less than two years later represent a remarkable recalibration; yet she is doing no more than sniffing the political air and realizing that the winds have shifted.
British Prime Minister Theresa May is doing the same. In June last year, while still a senior cabinet minister in David Cameron's government, she campaigned against Brexit.
But since becoming Prime Minister, she has sounded more in favor of a so-called "hard Brexit" than the official Leave campaign, and more like Nigel Farage and his anti-Europe, anti-immigration UK Independence Party.
May's apparent Brexit priority is controlling immigration. Business comes second, and yet, as there is no groundswell of buyer's remorse
, she still seems to be sniffing the political wind correctly.
It is becoming increasingly clear in Europe that a significant part of the electorate looks across the Atlantic and likes what it sees.
Were Le Pen to win the presidency in France, she would likely begin the process of untethering France from its European partners by changing the currency and calling for a Frexit vote.
Similarly in the Netherlands, Wilders would also try to take the country out of the EU.
That he is unlikely to succeed has nothing to do with his popularity on the streets and everything to do with the fractured nature of Dutch politics.
Even if his party does get more votes than any other in the Parliament, no other party would partner with him to bring him to power.
What happens in Holland and France paints only part of the picture. More than a dozen other European countries also have elections this year: Hungary, the Czech Republic and Denmark, to name but three. Each has its own popular, anti-migrant movement.
Nationalists are trading on the same fears that nationalists have always exploited: distrust of outsiders. In Europe today, radical Islamist terror, the human exodus from wars in the Middle East and the EU's free movement of people within its borders are proving a perfect combination for the right-wing populists.
Sixty years ago, when Europe's leaders first sought to bind their national economies together, decreasing the rationale for war, they were fresh from the lessons of World War II and needed no history books to point them in the right direction.
They had survived the war and knew the price that had to be paid. Today, there are fewer voices and the lessons of history are dimming.
While no one predicts a return to the horrific slaughter and appeasement of that dark chapter from history, some of the hallmarks of the intolerance that were its precursor can be seen.
In Europe, hate crime is on the rise. In the aftermath of the Brexit vote, a Polish man was killed in an attack that police are treating as a possible hate crime
. Since January, we have been reading more and more about anti-Semitic attacks and vandalism in the United States.
History shows us again and again that the more leaders identify immigration as a problem, the more immigrants pay a price.
But history can only partially prepare us for what is happening. In 2017, the anti-establishment populists come in different shapes and sizes.
Late last year, Italians voted against their Prime Minister Mateo Renzi in a referendum on constitutional reform
. Though his party is still in power, the effective winner was Italy's anti-establishment Five Star Movement
Around the same time, in Austria's presidential election, the nationalist candidate lost not to a mainstream candidate, but to the Green Party candidate.
In Holland, one of the challengers to populist Wilders is from another outsider, Alexander Pechtold of D66
: a different kind of populist who advocates for abortion, euthanasia, prostitution and marijuana use.
Europe's political jigsaw is a picture in transition: the traditional red and blue hues shading the left and right divide are being replaced. In Iceland, following months of traditional parties trying to form a government, the Pirate Party has been passed the political baton. They advocate the citizens' direct participation in democracy, everyone voting on all decisions -- big and small.
It's an idea that may not have come of age yet, but the seed has been planted. Five Star and D66 have similar aspirations.
Europe is not so much at a crossroads, as a terminus. The status quo appears to be over. Postwar political certainties that for so long seemed as solid as the Berlin Wall are collapsing and are being discarded.
There is no shortage of trains departing for other destinations. Some offer swift transit to liberal utopias; others offer rides to the past.
The common thread running through so many European countries is ironically something that inevitably divides them: nationalism.
This nationalism is being used to paint the leaders of Europe as an elite that has sold national values down the river in favor of globalization and the European project, much the same arguments Trump used to win his way to the White House.
How his conversation with Merkel goes next week could cast a long shadow over the polling booths of Europe. What happens there in the coming months will tell us a lot about what to expect over the next few years.
Voters would do well to reflect on history, listen to some seasoned voices before their recollections fade and the illumination they offer sputters out, leaving the old continent in the dark. As with Brexit, once selected, there is no easy turning back.