For a sign of how far Western politics and transatlantic relations have changed, look no further than this week's D-Day commemorations in Britain and northern France.
Five years ago, for the 70th anniversary, former US president Barack Obama traveled to France to stand with America's allies and deliver a moving tribute to their joint sacrifice and shared destiny in World War II.
In what was condemned as vulgar and disrespectful by right-wing opponents at the time, he was filmed chewing gum during one of the ceremonies -- apparently to stop a craving for a cigarette.
Starting on Wednesday, U.S. President Donald Trump will attend two days of memorials in Britain and France for the 75th anniversary of the world's biggest naval operation, which signaled the start of efforts to liberate western Europe.
"It's not the same world," Francois Heisbourg, a former French diplomat and head of the International Institute for Strategic Studies, told AFP.
While European leaders in Obama's era would sometimes complain privately that Europe was a low priority for the US president, none ever imagined a US leader actively working to undermine the European Union.
And Trump, who has cheered Brexit and is openly hostile to the idea of the EU bloc, has ripped up postwar conventions to such an extent that chewing gum at a ceremony seems like an offence from a different era.
He has publicly refused a handshake with German Chancellor Angela Merkel, called Canadian Prime Minister Justin Trudeau "weak" and has humiliated British Prime Minister Theresa May over her strategy to negotiate Britain's departure from the EU.
On his last visit to France in November last year to mark 100 years since World War I, he left mocking the "very low approval rating" of his host, President Emmanuel Macron.
Heisbourg said that "everyone will wait anxiously for the end of the ceremonies fearing a Twitter storm from Donald Trump."
Despite all this, Jeremy Shapiro, an expert on transatlantic relations at the European Council on Foreign Relations, said that relations between the US leader his Western counterparts "aren't disastrous".
"They still want to be allies, but there isn't that same sense of shared destiny which is what you need to land people on a beach together. There's a sense that they can have transactions that work," he told AFP.
"Trump has caused everyone to see him in that light, and that's how they see him," he added.
The commemorations of the D-Day landings, which saw 150,000 Allied soldiers storm the beaches of northern France on June 6, 1944, will begin on Wednesday morning.
Queen Elizabeth II will preside at a ceremony in Portsmouth in southern England attended by May, Macron, Trudeau, Merkel and Trump, who begins a state visit to Britain on Monday.
Thousands of ships left from Portsmouth under cover of darkness 75 years ago for an invasion that signalled the start of the liberation of western Europe from Nazi occupation.
British authorities have said the D-Day event will be "one of the greatest British military spectacles in recent history" involving 26 RAF aircraft and 11 Royal Navy vessels.
On Thursday, ceremonies in France will continue along the wide sandy beaches where troops faced a hail of Nazi bullets and artillery shells which left 10,470 dead, wounded or missing on the first day.
One notable absentee will be Russian President Vladimir Putin, who was invited to represent the Soviet Union for the first time in 2004 on the 60th anniversary of the invasion.
He was also present in 2014, just as his relations with the West were collapsing over his decision to order troops into eastern Ukraine to annex Crimea.
"In 2014, the attack in Crimea gave the Allies something to unite around," Heisbourg said.
The Russian leader, whose government made "sweeping and systemic" efforts to help get Trump elected in 2016 -- according to an investigation by US special counsel Robert Mueller -- was not invited this time.
European leaders and Trump are at odds on a number of issues, any one of which has the potential to become a public source of friction at this week's ceremonies.
The US leader has repeatedly threatened to impose new tariffs on European imports, and there are also major differences on climate change, Iran's nuclear ambitions and the civil war in Syria.
The sensitive issue of defense spending is seen as one possible flashpoint, given the occasion and Trump's past comments.
The U.S. president regularly assails European leaders for their failure to spend the equivalent of 2% of their GDP on defense.
The figure was agreed by all members of the NATO alliance, which grouped the Allies together after WWII, while Obama was still in office.
"There's a high risk that Donald Trumps uses the ceremonies to remind everyone about the dependence of Europe on the United States for its security and defense," Heisbourg said.
A source in the French presidency said Macron was hoping to use the opportunity to bridge some of his differences with Washington.
The D-Day commemorations are a "good opportunity to celebrate this common victory and to explore some of the priority issues between us to try to bring our positions closer together," an aide said on condition of anonymity.
This article was written by Adam Plowright and Daphne Benoit from Agence France Presse and was legally licensed through the NewsCred publisher network. Please direct all licensing questions to firstname.lastname@example.org.