BERLIN — Just off a wide boulevard in a leafy west Berlin suburb, the U.S.-German friendship is alive and well.

Americans play football, sail and dance with their German friends. The decades-old bond between the two countries is on full display.

Trouble is, it's only a display. Opened in 1998, the Allied Museum, a free exhibition housed in an old U.S. Army theater, offers a window into what once was — and a welcome escape from what is.

Nearly 75 years after the end of World War II, the U.S.-German relationship isn’t just moribund, it’s on life support.

At both the official and unofficial level, the foundation that has supported the transatlantic alliance since the 1950s is crumbling. About 85 percent of Germans consider their country’s relationship with the U.S. to be “bad” or “very bad,” according to a recent study, while a clear majority want Germany to distance itself from the U.S.

“I have German in my blood” — Donald Trump

Angela Merkel is in the United States this week for the United Nations climate conference but a meeting with the U.S. president, who is also in New York, is not on her agenda. Merkel didn’t see Trump during her last visit to the U.S. in May either.

While Merkel visits the U.N., her heir apparent, Defense Minister Annegret Kramp-Karrenbauer, is in Washington, where she is expected to face more tough questions at the Pentagon over German defense spending.

The fraying of ties — which began long before Trump came to power but has accelerated since — carries implications that stretch far beyond the two countries’ bilateral relationship. With China seeking to expand its influence in Europe, and Russia eager to exploit the transatlantic rift, the disintegration of German-American unity would have profound implications for the future of NATO and the broader global order.

That might be why both sides are trying to pretend everything is OK.

“I have German in my blood,” Trump, who has treated Germany like a piñata since he took office in 2017, said during a brief encounter with Merkel at the G7 meeting in France last month. He added he would be “very honored” to visit her in Berlin, while acknowledging he has no firm plans to do so.

Trump’s sudden affinity for the land of his forebears triggered an audible guffaw from Merkel, who did her best during their joint press conference to keep a straight face.

“It’s not a problem for us to address difficult topics with one another,” she insisted.

More worried than wunderbar

Berlin is so worried about the deterioration in the ties with its biggest trading partner that Germany's Foreign Office is funding a special initiative dubbed "Wunderbar Together," a yearlong series of events across the U.S. meant to remind Americans how much the two countries really like one another.

Merkel's role in America's culture wars, where — depending on the stage — she plays either the villain who opened the floodgates to uncontrolled Muslim migration, or the saint who rescued people in need, has complicated Germany's PR effort. That was apparent during the German leader's May visit, when she was celebrated like a lost savior during her commencement speech to Harvard graduates.

Merkel appeared to revel in the adulation. Whether it helps Germany, which depends on the U.S. both in economic and strategic terms, to have its leader at the center of America's partisan battlefield is another question.

Germans' attitude to Trump is much more straightforward: They universally dislike him.

When it comes to relations between nations, most Americans continue to have a positive view of Germany — in contrast to Germans' opinion of the U.S.

But the “difficult topics” that Merkel referenced dominate the official conversation. Whether the question is Iran, trade, defense spending or climate change, Berlin and Washington are at loggerheads. Even in areas where strategic logic should make them natural allies — such as confronting China’s growing influence — the two have failed to move beyond their differences.

It’s tempting to blame the troubled relations on Trump’s withering attacks on Germany. His riffs on Germany’s tepid defense spending, its chronic trade surpluses and “Ahngula’s” migration policies are among the highlights of his rhetorical repertoire.

„Angela, Angela, you have to pay your bill.“ Donald #Trump unplugged – über sein Verhältnis zu den Deutschen. pic.twitter.com/T2JyV7GTR4 — Gabor Steingart (@gaborsteingart) July 19, 2019

“In contrast to every other president before him, Trump has created the impression that partnership amongst equals isn’t desired,” former German Foreign Minister Sigmar Gabriel, who now heads the transatlantic lobbying group Atlantik Brücke, told me recently.

In truth, the U.S.-German alliance has never been a partnership of equals. Tension has been part of the mix throughout the post-war era to varying degrees. If Konrad Adenauer and John F. Kennedy shared a mutual dislike, Helmut Schmidt and Jimmy Carter absolutely despised one another.

From the 1960s until the end of the Cold War, Germans took to the streets in droves to voice their opposition to both the U.S. war in Vietnam and the arms race with the Soviets.

Even so, this time, things really are different. And that's not just down to Trump.

People power

For decades the German-U.S. relationship was sustained not just by military alliances and business interests, but by personal bonds. Even Germans critical of the U.S. agreed that American engagement was better than the alternative. At times of tension and disagreement, most Germans gave America the benefit of the doubt.

Over the course of the Cold War, millions of American soldiers were stationed in Germany, where many married and had children. Untold thousands of German teenagers went to the U.S. as exchange students and countless more studied at U.S. universities.

With the fall of the Berlin Wall, the number of U.S. military personnel fell dramatically from nearly 250,000 in 1985 to about 35,000 today. Though the U.S. remains a favorite destination for German high schoolers, the number of exchange students heading across the Atlantic has dropped by about 30 percent since 2009 to fewer than 6,000.

As the U.S. troops have gradually withdrawn, the residual gratitude many Germans felt over their presence has also evaporated.

During my first posting in Germany as a correspondent in the mid-1990s, the Germans I met brimmed with enthusiasm for all things American and were full of stories of their adventures there. Even if they took issue with many U.S. policies, there was a reserve of goodwill, a sense that we were all on the same side.

When the subject comes up these days, it’s like walking on eggshells.

“My father was a big fan of the U.S. and its democracy,” a new acquaintance told me recently, making it clear that he didn’t share his father’s perspective.

The German distrust began to take hold in the aftermath of 9/11. Though Germany joined the U.S.-led coalition in Afghanistan against the Taliban, Berlin refused to participate in the Iraq War, arguing there wasn’t enough evidence to support claims that Saddam Hussein had stockpiles of weapons of mass destruction.

While Germany’s decision under then-Chancellor Gerhard Schröder proved to be prescient, it also left a wound that has never fully healed. In recent years, Germany’s view of the U.S. has been framed by Guantanamo, NSA spying and Trump’s attacks.

Those issues made it easier for Germans to ignore persistent U.S. demands that Berlin reduce its massive export surplus, which most economists agree exacerbate global imbalances, or that it meet the NATO defense spending target. The last two U.S. administrations also pressured Merkel's government to spend more on security, albeit with little success. Trump, on the other hand, appears to have gotten the Germans' attention.

But Trump's relentless pressure campaign has come at a cost at street level.

“At the moment, Trump is the dominant factor in the transatlantic relationship” — Wolfgang Ischinger, former German ambassador to Washington

For almost 60 years, Germans and Americans have celebrated their friendship with an annual Volksfest, an open-air fair with a replica town from the Old West, hotdogs and American music. In July, the fest was canceled for the second time in three years after Berlin Mayor Michael Müller, who heads a leftist coalition, claimed to have failed to find a venue.

Just weeks earlier, Müller’s city government refused to allow 20 “Candy Bombers” — the historic U.S. transport aircraft used during the Berlin Airlift — to land at the city’s Tempelhof airport, citing local laws and safety regulations. Some of the planes had been flown over from the U.S. for the event.

What’s striking about such incidents is that few Germans seem to really care. A couple of newspaper writers expressed outrage over the Candy Bomber snub, but the story was quickly forgotten.

Even though the U.S. remains the guarantor of German security, for many Germans, both in and out of government, America is just another partner, not a true friend. Travel-obsessed Germans still visit the U.S. by the millions on vacation, to enjoy the beaches in Florida or the sights of New York. Just like they go to Turkey, another erstwhile German friend with whom relations have soured.

Recent suggestions by U.S. officials that Washington might transfer its German-based forces to Poland were met with a collective shrug in Berlin. Even though most German officials viewed it as an empty threat, some joked that losing the bases might be worth it if it took Germany out of Trump’s crosshairs.

With official German-U.S. relations at such a low point, it’s been left to a small band of die-hard believers to keep the transatlantic flame burning.

“At the moment, Trump is the dominant factor in the transatlantic relationship,” said Wolfgang Ischinger, the former German ambassador to Washington who now heads the Munich Security Conference, an annual forum that has been a fixture of the transatlantic dialogue for decades.

Ischinger does not believe the the U.S.-German alliance can return to the “status quo ante” after Trump’s presidency, but he said he hasn't given up hope on a relationship that delivered his country from tyranny and returned it to prosperity.

“George W. Bush wasn’t that popular in Western Europe either,” he told me. “But as soon as Barack Obama emerged as a candidate, 200,000 people ran to Berlin’s Victory Column to listen to him speak and to cheer. Suddenly, America was highly popular again and our entire nation was excited.”

If all else fails, that could be the final exhibit in the Allied Museum.

Matthew Karnitschnig is POLITICO's chief Europe correspondent, based in Berlin. He began reporting on Germany in 1997.