Donald Trump didn’t invent the American tradition of ditching our friends like a bad prom date (ask the Kurds, Afghan interpreters or anyone who sat through “Rambo: First Blood Part II”). But since returning to office, he’s taken this all-too-frequent bad habit and made it official U.S. policy.

The latest example? Trump’s conclusion that Volodymyr Zelensky, the leader of Ukraine — you know, the country currently being turned into rubble by Russian missiles — is “not ready for peace” and that he “disrespected the United States of America.” This latter statement (made live on TV during a heated Oval Office meeting), came on the heels of Trump taking to social media to call him a “dictator.”

If irony were a renewable energy source, Trump’s rhetoric could power the United States for a century. Because while Trump throws Zelensky under the bus, his real crush, Vladimir Putin — the guy serially accused of poisoning journalists, the guy whose critics tend to end up dead, jailed or exiled, the guy who wins “elections” by suspicious, predictable landslides — is out here running an actual dictatorship. His troops are raping Ukrainian women, according to investigators; his forces are kidnapping children and flattening cities. But yeah, the real problem is the elected leader trying to stop them.

It would be hard to overstate how rapidly this relationship has fallen apart. In case you missed it, Trump took it upon himself to negotiate Ukraine’s fate without having Ukraine in the room. His team also floated an “offer” to Ukraine straight out of “The Godfather”: Hand over some mineral rights as “payback” for our past help, and maybe we’ll think about letting you keep defending your country. Maybe.

And if that wasn’t humiliating enough, during that aforementioned Oval Office meeting, Trump and Vice President JD Vance escalated things to a new low, staging a televised Oval Office attack on Zelensky in a spectacle more suited to the WWE than international diplomacy.

During the exchange, Vance called Zelensky “disrespectful” and said he should be more thankful to Trump. The clash, broadcast for the world to see, wasn’t just a political power move — it was a calculated act of degradation, reinforcing the message that under Trump, Ukraine is expected to grovel for every bullet. It was a diplomatic disaster and a propaganda gift to Moscow, all rolled into one.

Never mind the fact that we assured Ukraine (before and after Russia’s invasion) that we’d have their back. If we break that promise now — as it appears we are poised to do — the consequences won’t stop at Kyiv. The message will travel far beyond Ukraine to our allies (who are watching nervously) and our enemies (who are taking notes).

For the better part of a century, America’s foreign policy has boiled down to this: We foot most of the bills and prevent bullies from rolling over weaker sovereign states. In return, we get a world that (mostly) behaves itself.

Trump, however, looks at this mutually beneficial deal and assumes he’s getting “scammed.” He views NATO like a group dinner where everyone else orders lobster, and he thinks he’s stuck with the bill.

Why should we pay for security? Why should we defend our allies?

Uh, because it keeps the world from becoming a flaming dumpster fire.

The alternative is far worse: Allies either rearm (including nukes) or they start making new, less-savory friends. Neither scenario ends well for the U.S.

Let’s talk about our allies. Germany is rearming, which — if you’ve read even a single history book published after 1945 — might make you a bit uneasy.

That said, the free world may need Germany to step up if the U.S. retreats from the global stage like Homer Simpson disappearing into the bushes.

“My absolute priority will be to strengthen Europe as quickly as possible so that … we can really achieve independence from the U.S.A.,” Germany’s chancellor-in-waiting Friedrich Merz said before the final results of his election were even announced. “After Donald Trump’s statements last week at the latest, it is clear that the Americans … are largely indifferent to the fate of Europe.”

Among the most recent statements, Trump claimed: “The European Union was formed in order to screw the United States. … And they’ve done a good job of it.” In reality, as a bloc, the EU represents our largest trading partner.

It’s not just Europe. Longtime friends Australia, Taiwan and Canada (or as Trump calls our neighbor, America’s 51st state) are starting to look around and get nervous. Even Japan — yes, that erstwhile empire we politely asked not to conquer the Pacific ever again — has begun since the first Trump administration to stock up on weapons like there is an apocalypse fire sale.

All of this marks a rather stark departure from the nuclear umbrella and post-war liberal order that — barring a few notable exceptions — has let Americans enjoy a blissful, air-conditioned peace, complete with two-car garages, well-manicured lawns and shopping malls since 1945.

But hey, who needs stability when you can have excitement? After all, maintaining these alliances took effort. For one thing, you have to keep sucking up to people who aren’t as strong as you, and probably aren’t chipping in as much cash as they might.

Take, for example, President Reagan’s speech commemorating the 40th anniversary of D-Day. I remember hearing it as a boy and thinking, “Why all the talk about the Allies?” I mean, Reagan raves about the “impossible valor of the Poles,” “the forces of Free France” and the “unsurpassed courage of the Canadians.” And he throws in seemingly extraneous references to British troops hearing bagpipes and to Lord Lovat of Scotland.

Why? Because back then, we knew the world worked better when our friends believed we were in this existential struggle together. Trump seems to be going out of his way to send the opposite message: You’re on your own!

But the biggest reason that abandoning our allies is dumb can be summed up in one word: China. You remember China, right? The country that sends us fentanyl and TikTok propaganda and outnumbers us four-to-one? Well, guess what — if the free world sticks together, we pretty much match them in population, land and strength. But only if we stick together.

Trump, the so-called greatest dealmaker, is out here making the worst deal in American history by giving away U.S. influence, alienating allies, gutting American soft power by dismantling foreign aid and handing power to the people who really want to screw us. Nothing says “America First” like leaving your friends dead last. And here’s the thing: It’s easy to fritter away our power, but it would be a decades-long struggle to regain influence once it’s gone.

How does a super power lose its moral authority, allies and standing in the world? Slowly … and then all at once.

Matt K. Lewis is the author of “Filthy Rich Politicians” and “Too Dumb to Fail.”