There was a time, not so very long ago, when the US was held up as a model for other nations to emulate. That time has passed. Last week witnessed more gratuitous international hooliganism by the Trump administration. Its latest depredations include extra-territorial bullying of trade and business rivals, violent threats against Iran, an absurdly biased “peace plan” for Palestine, resumed arms sales to fuel the Saudis’ war in Yemen, and an assault on global press freedom.

Anger and dismay over Donald Trump’s wildly swinging wrecking ball obscure they ways in which the US could be using its unmatched power to benefit others – but refuses to do so. Its current policy is defined by its absences. Once again, Syrian civilians are dying in a horrific war Trump has done nothing to halt. Alarm bells are ringing over the climate crisis and mass extinction – yet Trump’s people prefer to focus on economic opportunities afforded by a melting Arctic ice cap.

The US once stood in the vanguard of western states promoting democratic governance and respect for universal human and civil rights. Its record was imperfect, but at least it tried – most of the time. Under Trump, authoritarian regimes from Russia and Egypt to Brazil, the Philippines, North Korea and Myanmar are not only tolerated, they are positively encouraged. Progressive forces that counted on American support, and the American example, can no longer do so.

Nowhere is this more evident than in Sudan right now, where the people’s revolt that began last December against Omar al-Bashir’s military-backed regime is at risk of failing. Despite its size and strategic importance, Sudan receives scant attention in the west. Yet when consideration is given to its passionate quest for democracy, its internal struggles with Islamists, and the possibility it could explode into civil war, like Syria, Libya and Yemen, that neglect looks short-sighted.

The US record in Sudan is mixed. Bill Clinton bombed Khartoum in 1998 over alleged connections with al-Qaida. Washington helped broker the 2005 comprehensive peace agreement that foreshadowed South Sudan’s independence. Until recently, it maintained sanctions on the regime. Now, with Bashir under arrest and the military off balance, a rare chance has arisen to help move Sudan firmly into the democratic camp. Yet what is the US doing? If anything, it is pushing the other way.

Foreign diplomats and analysts describe US policy as confused or non-existent. Relations between the Sudanese Professionals Association (SPA), the opposition’s organising force, and the US embassy in Khartoum are said to be strained. One opposition official told Foreign Policy magazine that talking to the Americans was “a waste of time”. A meeting in Washington earlier this month of western countries, the UN and the African Union failed to agree a joint course of action.

Rather than seize the moment, the US (and by default, Britain, the former colonial power) has passed the initiative to Trump’s hard-faced buddies in Saudi Arabia, Egypt and the UAE. These countries backed Bashir and are now backing (and financing) attempts to revive the pre-coup status quo under new leadership. Sudan’s protesters were clear from the start that the regime, and not just its senior figures, must change. It is this crucial battle they are in danger of losing.

This ultra-conservative, nationalist Arab axis, marching in ideological lock-step with Trump, has its own candidate for Sudan’s next strongman. General Mohammed Hamdan Dagalo, known as Hemedti, is deputy leader of the transitional military council. He also heads the feared Rapid Support Forces (RSF), a large paramilitary group that evolved from the Janjaweed militia implicated in the Darfur genocide. Sporadic, lethal attacks on street demonstrators earlier this month were blamed on the RSF.

Dagalo has easily eclipsed the head of the military council and Sudan’s temporary leader, General Abdel Fattah al-Burhan. It was Dagalo’s insistence on having an inbuilt majority in a proposed civilian-military power-sharing government that triggered last week’s breakdown in talks with the opposition. And when the SPA called a general strike in response, it was Dagalo who threatened reprisals. It is unclear what the opposition, split over tactics and running out of steam, can do now. The danger of a descent into violence is real and ever-present.

The shining city on a hill has, in the era of Trump, become a darkly tarnished keep from which to browbeat the world

Dagalo claims he is not seeking power, but his ambition is obvious. He said last week he was overseeing judicial proceedings against Bashir and 25 regime figures detained since the coup – thereby controlling the process and ensuring they pose no threat to the new order. At the end of the week, he personally received the royal seal of approval from Trump’s principal Arab ally, Mohammed bin Salman, the Saudi crown prince, at a private meeting in Jeddah.

Outsourcing US foreign policy to Trump-like “strongmen” and friendly regional proxies is now an established trend. In neighbouring Libya’s rekindled civil war, Trump backs a renegade general, Khalifa Haftar, who is also supported by the Saudis and UAE. Likewise, the White House gave a warm welcome to Egypt’s president, Abdel Fatah al-Sisi, another instinctive autocrat who hijacked a popular revolution. As in Sudan, hopes of root-and-branch reform in Algeria, where a figurehead president was forced out last month, are fading amid army machinations and American and European indifference.

Perhaps it is incorrect to say the US no longer leads by example. A depressingly large number of world leaders now take their cue from Trump, aping his regressive, self-serving and adversarial outlook.

The totemic American founding vision of “a shining city on a hill”, symbolising a land of freedom and justice, has in the era of Trump become a darkly tarnished keep from which to browbeat, exploit – or ignore – the world.