Over the next two days, the 75th anniversary of D-Day will be marked with solemn salutes for the undaunted courage of individual soldiers and sailors and the inspired leadership that assembled the armada that liberated Europe.

President Trump will take part in ceremonies in England and then in Normandy, France, where the German bunkers, bomb craters and the vast American cemetery stand in silent testament to the great alliance that came ashore and defeated Hitler.

Indeed it was great, perhaps the greatest wartime alliance in history, but could it be done again? If, God forbid, another Hitler were carving up Europe like warm bread, would a new international force respond to storm the beaches and save civilization?

Merely to ask the question is to suggest the unhappy answer. The West ain’t what it used to be.

This will come as news to many in London, Paris, Berlin, Amsterdam and Brussels, but Donald Trump didn’t cause the decline of the West. In fact, among his supporters, the decline of America largely explains why he was elected in the first place.

Yet to hear the London demonstrators and some foolish British politicians, Trump is the biggest problem in the world. If it weren’t for him, the lion and the lamb could lay down together.

Sure, all you would need is a new lamb each morning.

The modern world as we know it was born in the aftermath of World War II. Unprecedented levels of peace, prosperity and democracy spread across the globe and were guaranteed by financial and military institutions funded mostly by America.

But vigilance waned as memories dimmed, and much of Europe used the continent’s longest holiday from war to disarm and expand their welfare states. They assumed, correctly, that America would be there to protect them.

Then along comes Trump with his America First agenda and instantly he’s the skunk at their garden party. He demands, outrageously in their view, that Europe finally pay its fair share for the common defense, a promise often made but never kept.

They hate his insistence on border security, even as their nations are roiled by their own influx of uninvited migrants. They hate him for this and they hate him for that, but most of all, they hate him for being so damn American.

Give us a citizen of the world, they say, give us another Barack Obama. Give us somebody who flatters us and apologizes for America.

This hatred can appear to be a kind of sport for hooligans, with loud chants, quiet snubs and occasional milk shakes the weapons of choice. But this is no game.

The alienation is so deep and destructive that if Trump were at the helm of a new alliance in a time of global crisis, many of our old allies would spend their energies demonstrating against him and spewing nonsense, but few would pick up a gun or encourage others to do so. They would rather lose than fight beside him.

Trump Derangement Syndrome, you see, has gone international. He doesn’t deserve a state visit or even common courtesy because, according to London Mayor Sadiq Khan, America’s president “stands for the complete opposite of London’s values.”

Right, London’s values. Asian autocrats, Mideast butchers and Russian oligarchs are welcomed there with open arms, but the president of the United States is treated too often like a Third World thug.

Trump got it exactly right when he called Khan a shorter version of Bill de Blasio.

The anti-Semitic leader of the opposition Labour Party, Jeremy Corbyn, boycotted the state dinner but appeared at a demonstration protesting Trump’s presence. Corbyn has laid a wreath on the graves of Arab terrorists and compared Israel to Nazis, but Trump is beneath him.

Prime Minister Theresa May, on her way out the door, behaved impeccably in hosting Trump, as did Queen Elizabeth and those in the royal family who understand what America means to the world.

But the likes of Khan and Corbyn stain historic memory and embarrass their nation. They are the ignorant elite, seeing a hamstrung America — and a diminished Israel — as good for the world.

They view their fellow countrymen who support Brexit as the British equivalent of deplorables.

They are not alone.

Consider that on the eve of Trump’s trip, German Chancellor Angela Merkel gave the commencement address at Harvard and got standing ovations for obvious criticisms of America’s president, though she never used his name. Naturally, Merkel also got applause from the American media for taking on the president they love to hate.

In another era, no foreign leader would dare think of coming to America to insult our president. But the “anything goes” habit has become so routine in the age of Trump that Merkel’s insufferable lecture came and went without much notice.

In Washington, mad-dog Democrats also threw off bipartisan traditions and good manners. Even as the president was out of the country, they continued to air their fantasies of deposing him, with some advocating a climb-the-ladder approach of first impeaching much of his cabinet.

Attorney General William Barr is at the top of their enemies list, a desperate-for-attention 2020 candidate called for the impeachment of Treasury Secretary Steven Mnuchin, and others want Commerce Secretary Wilbur Ross to face the same music. They’ll come up with reasons later.

Two leaders of the House impeachment caucus, Rep. James Clyburn and Rep. Jerry Nadler, explained that they were going slowly because the public polls showed wide opposition to impeaching the president. So first, they’re going to have a trial and then hang him.

Clyburn said various committee investigations would “effectively educate the public” while Nadler put it this way: “The American people, right now, do not support it because they do not know the story. They don’t know the facts.”

Ah, yes, the rubes, bitter clingers and irredeemables should shut up and listen as their government betters instruct them in the inscrutable meaning of “high crimes and misdemeanors.”

Ironically, such fundamental unseriousness is made possible by the great victory achieved 75 years ago. You don’t have to romanticize war or the ordinary people who fought it to imagine how the 2,499 Americans who died on D-Day would view their nation today.