Donald Trump made 30,573 “false or misleading” claims during his first term, according to calculations published in 2021 by the Washington Post. That’s roughly 21 fibs a day. Second time around, he’s still hard at it, lying to Americans and the world on a daily basis. Trump’s disregard for truth and honesty in public life – seen again in his despicable response to the fatal shooting in Minneapolis – is dangerously immoral.

Trump declared last week that the only constraint on his power is “my own morality, my own mind”. That explains a lot. His idea of right and wrong is wholly subjective. He is his own ethical and legal adviser, his own priest and confessor. He is a church of one. Trump lies to himself as well as everyone else. And the resulting damage is pernicious. It costs lives, harms democracy and destroys trust between nations.

Like US voters, foreign leaders have grown accustomed to the president’s chronic mendacity. But the price for indulging it, for not calling it out, for not taking a stand rises exponentially as his behaviour becomes more dictatorial and erratic. Trump’s lies and deceptions are a common aggravating factor in three intractable present-day international crises.

He falsely claims, for example, that Chinese and Russian warships are “all over the place” in Greenland, necessitating a US takeover. Ahoy there! What ships? asks Denmark’s foreign minister, Lars Løkke Rasmussen – who, unlike Washington’s empire-builder, has first-hand knowledge of the self-governing island. Greenlanders dismiss Trump’s comments as nonsense.

Denmark points out it spends billions in Greenland and that a supposed flood of Chinese investment is another White House whopper. Polls show Greenlanders oppose annexation or sale to Trump. They prefer independence, which the US, celebrating 250 years since it rusticated King George III, might be expected to understand. Trump says he wants to secure Greenland. In truth, he wants to secure its mineral riches – and make America bigger again.

A veritable torrent of lies preceded last weekend’s Venezuela coup. Trump claimed, without evidence, that the country’s leader, Nicolás Maduro, was a “narco-terrorist” cartel boss. His administration killed more than 100 people in boats in the Caribbean Sea and Pacific Ocean on unsubstantiated suspicion of drug-smuggling. He falsely declared the US to be at war, illegally usurping Congress’s constitutional authority.

Truth is, Trump has pursued a personal vendetta against Maduro since his regime change plot failed in 2018. Truth is, as Trump now admits, the coup’s main aim is not to restore democracy – though he’s belatedly agreed to meet the opposition leader, María Corina Machado. It’s not to “rescue” Venezuela’s people, or safeguard US security. The aim is the oil. Trump is shamelessly, ruthlessly looting the country while threatening Mexico, Cuba and Colombia, too.

Trump says he has a “plan” to run Venezuela indefinitely. That’s another porky pie. With its armed forces and militias intact, with the repressive Maduro regime still in place, and with an emboldened democratic opposition determined to win power, the country is heading for a showdown. Only deeper, protracted US military intervention – which Trump is toying with – may halt a slide into chaos. He’s risking a Balkan quagmire on Washington’s Latin American doorstep.

Talking of quagmires, spare a thought for Ukraine – a third conflict zone where Trump’s inability to distinguish right from wrong, to tell truth from lies, does huge harm. Trump lied when insisting he could easily end the war with Russia in 24 hours. Thwarted, he has repeatedly promised to get tough with Vladimir Putin. Time and again, that smirking villain – another inveterate liar – has deftly humoured him, then resumed bombing. Time and again, Trump feebly backs down, usually blaming Ukraine’s blameless leader, Volodymyr Zelenskyy.

Trump’s duplicity undermines allied efforts to sustain Kyiv’s struggle. One day he smugly accepts the greasy plaudits of Nato leaders; its secretary-general, Mark Rutte, calls him “Daddy”. The next, he mocks the alliance and says Europe faces “civilisational erasure”. Last week he claimed Nato would not help the US in an emergency. Another lie. That’s exactly what it did after the 9/11 terror attacks and during 20 years of blundering in Afghanistan.

Today’s concurrent crises – Greenland, Venezuela and Ukraine – share other factors in common, Trump’s dishonesty aside. In all three cases, the weakness and divisions of European leaders, and of the EU as an institution, have been alarmingly exposed. Surely now, finally, Europe must accept it cannot trust or rely on this president. In this daunting geopolitical context, Brexit no longer looks like just a stupid mistake. It looks almost suicidal.

Disrespect for international law, the flouting of sovereign rights and territorial independence, and the ongoing replacement of the UN-backed rules-based order with neo-imperial spheres of influence are evident in all three crises. So, too, is a failure to defend the democratic rights of ordinary people. The US has presumptuously, illegally ruled out elections in Venezuela. Russia is trying to kill Ukraine’s democracy. Greenlanders say they alone must decide their future. But who’s listening to them?

Many of these broader trends were already well established. Yet Trump’s destabilising, unprincipled, lawless, chaotic and fundamentally immoral carrying-on in 2025 has undoubtedly acted as catalyst and accelerant. Of all these ills, his moral turpitude is the greatest. It corrupts, bedevils, darkens and poisons the humanity of the world. It is toxic to all it touches. Trumpism is a corrosive disease. Its latest victims are in Minneapolis and Portland. In truth, they are everywhere.

To mangle Mark Twain: “There are three kinds of lies: lies, damned lies, and Donald Trump.” Americans and their too-diffident friends in Britain and Europe must be more forceful in speaking truth to power – before, like the much-reviled George III, Trump does something really crazy.

Simon Tisdall is a Guardian foreign affairs commentator