As usual, Mike Pompeo was brutally frank. Speaking in London last month, the US secretary of state warned that future bilateral intelligence sharing would be at risk if Britain allowed the Chinese telecoms giant Huawei access to its new 5G rollout. “The US has an obligation to ensure the places where we operate [are] within trusted networks, and that is what we will do,” he said.

The issue might appear arcane. But Pompeo’s threat, which Donald Trump will reiterate during his state visit, beginning on Monday, sent a chill through the diplomatic, defence and security establishment. In an age of rapidly diminishing influence, Britain still prides itself on its intelligence gathering, counter-terrorism and counter-espionage capability, as well as agencies such as GCHQ and its new offshoot, the National Cyber Security Centre.

This capability is recognised and respected – and is a main reason why Washington maintains a close alliance. Britain brings something substantial to the top table – and that helps secure its place there. By publicly questioning this collaboration, Pompeo thrust a well-aimed dagger into the heart of the “special relationship”.

He surely knows retaliatory US curbs on reciprocal intelligence sharing would deal a severe blow to Britain’s reputation as an in-the-loop country. MI6 could find itself out in the cold. And one of the last remaining justifications for 75 years of meekly doing Washington’s bidding would be blown away.

Trump and Pompeo’s crude attempts to dictate terms is of a piece with a dramatic deterioration in US-UK diplomatic and security relations across multiple fronts. One obvious cause is Trump’s corrosive behaviour. But the crisis is also rooted in profound political shifts in both countries – and in an international order that is increasingly spinning beyond their control.

Trump’s disruptive, adversarial “America First” approach to key foreign policy issues is a particular problem for Britain. Foreign Office diplomats past and present recently assured the House of Lords select committee on international relations that healthy long-term ties did not depend solely on individual presidents or prime ministers. Like all things in life, Trump, too, would pass.

But that serious damage has already been done is not in dispute. “The US has taken a number of high-profile unilateral foreign policy decisions that are contrary to the interests of the UK,” the committee said in a report, UK Foreign Policy in a Shifting World Order, debated in the Lords last month.

“US withdrawal from the Paris agreement on climate change, the Iran nuclear deal and the United Nations human rights council, and the imposition of trade tariffs on its allies, undermine efforts to tackle pressing global challenges of critical importance to the UK.”

The list of joint policy positions smashed by Trump’s wrecking ball is, in fact, much longer, and fundamentally challenges long-established British policies, interests and values. In the Middle East alone, the list includes impetuous US threats to wage war on Iran; unbalanced attempts to impose a settlement on Palestine, bypassing UN resolutions; a free hand for Washington’s autocratic Arab proxies in Yemen, Libya and Sudan; and an uncoordinated troop withdrawal from Syria, undertaken even as Isis regroups.

In terms of multilateral institutions and international law, the Trump effect has been similarly chilling for Britain. Nato, the linchpin of UK security, has been persistently undermined; Russia’s malign activities go largely unpunished. The UN security council and UN agencies are subverted or ignored. The global nuclear non-proliferation regime has been weakened as Trump tears up arms control treaties and upgrades weapons. And the International Criminal Court, which Britain helped create, has been effectively outlawed by Washington.

In all of this, the vaunted “special relationship” has been of little use in mitigating behaviour that is destructive of what used to be called shared values. In truth, Britain hardly dares breathe a word. Are Trump’s Muslim travel ban, his heartless persecution of migrants at the Mexico border, his coddling of Saudi Arabia’s murderous regime, his war on abortion rights, and his flirtation with Europe’s hard-right populists all actions that Britain supports? It’s hard to say, given Whitehall’s silence.

When a British general in Baghdad recently contradicted the White House’s unproven claims to have covert intelligence about an “imminent” Iranian attack, Jeremy Hunt, the foreign secretary, buckled under pressure from Washington and disowned him. The climbdown was consistent with decades of kowtowing that has encouraged, for example, Trump’s blatant interference in domestic British politics.

The all-party House of Lords report was Pompeo-like in its bluntness. The US would remain an important ally, it said, but Britain must understand that, in many respects, it could no longer be trusted; that on key issues, the Trump administration actively opposes the UK; that Britain should find new allies, such as India; and that it must not be sucked into a confrontation with China.

Is Washington’s shift permanent, or merely a blip? Probably the former. “Clearly, our American allies themselves are conscious that their own primacy, their unipolar moment, is now ended,” David Howell, a former Conservative minister and committee chairman, told the Lords. “This changed approach is deadly serious for us here. It means that the areas where our interests diverge from America’s are multiplying.”

Faced with exceptional Trump-era arrogance and ignorance – and unfavourable, seismic shifts in the global power balance– a weakened Britain needs the mutual support and solidarity of its democratic European partners more now than probably at any time in its history. It’s plain that knee-jerk subservience to an increasingly antagonistic, ill-led US distorts Britain’s sense of self and hinders its efforts to make its way in a changing world.

Trump, no friend of ours, should be given the heave-ho. It is time to take back control.