He did not shove the prime minister of Montenegro at a photo-op, he did not call the British prime minister and German chancellor “losers” and he did not deride Nato as a bunch of grifters looking for a free lunch.

So low was the bar set by former US president Donald Trump that, merely by condemning Russia’s Vladimir Putin rather than gushing over his biceps, Joe Biden earned good will on his unity and resolve tour of Europe.

The president came to Brussels on Thursday with promises to accept up to 100,000 Ukrainian refugees fleeing the month-long Russian invasion, give $1bn in new humanitarian aid and impose sanctions on 300 members of the Russian parliament.

It was an attempt to project reassurance that Biden, born during the second world war, can emulate President Franklin Roosevelt’s “great arsenal of democracy” without stumbling into a third.

But the 79-year-old’s handshakes and whispers with France’s Emmanuel Macron and others at the Nato, G7 and European Council summits may put the seal on the Obama paradox: an American president more popular abroad than at home.

Gallup surveys conducted before Russia invaded Ukraine showed the image of US leadership making a significant recovery from the Trump era. “Between 2020 and 2021, American leadership saw double-digit gains in 20 of the 27 Nato members surveyed both years,” the polling firm said.

That stands in vivid contrast with Biden’s approval rating within the US, which this week fell to a new low of 40%, according to a Reuters/ Ipsos opinion poll. The survey found that 54% of Americans disapprove of his job performance as the country struggles with high inflation.

Biden’s approval rating matched Trump’s at this point in his presidency: both stood at 40% in mid-March in their second year in office. The relief of western allies at having America back at the table is unlikely to be reflected by domestic voters in the midterm elections in November.

That is why Republicans are hammering away at Biden by urging him to do more for Ukraine though with few specific details and, more loudly and convincingly to the electorate, by blaming him for soaring gas prices at home. They intend to prove the old adage that all politics is local.

The point was illustrated on prime time cable news television on Wednesday night. CNN’s Anderson Cooper opened his show with coverage of the war in Ukraine; Tucker Carlson, on the conservative Fox News channel, talked instead about supreme court nominee Ketanji Brown Jackson declining to offer a definition of “woman” during her Senate confirmation hearing.

CNN’s Reliable Sources newsletter noted: “As Cooper showed horrifying drone footage of the widespread devastation in Mariupol, Carlson showed his audience a sex-ed type graphic of the female reproductive system.”

It observed: “Four weeks after the war commenced, there are signs that fatigue is setting in. TV news ratings, for instance, have started to fall back to reality after ballooning early on. And perhaps another sign is the return of culture idiocy that is once again saturating channels like Fox and social media feeds.”

It is a further reminder to be grateful that Trump no longer has his finger on the Twitter button – or the nuclear one. The man who once posed the biggest threat to global democracy has been replaced in that role by Putin. Biden beat one and must now thwart the other.

So far that has meant a “Goldilocks” approach – not too hot, not too cold, not too weak, not too provocative. This received a boost on Thursday when Ukrainian president Volodymyr Zelenskiy delivered a video address to Nato from Kyiv that did not, according to White House officials, include calls for a no-fly zone or Nato membership, giving Biden some breathing room.

Still, Zelinskiy naturally urged Nato to stiffen its spine and do more, and it remains unclear how Biden will respond if an increasingly desperate Putin resorts to biological, chemical or even nuclear weapons. Western unity will be tested as the costs of war bite into the global economy.

The German chancellor, Olaf Scholz, dismissed calls to follow the US by boycotting Russian energy supplies, warning: “To do so from one day to the next would mean plunging our country and all of Europe into recession.”

The president who made a contest between democracy and autocracy the guiding principle of his foreign policy will also be aware that Thursday’s meetings are being watched closely by China, which has sent mixed signals about the invasion and may yet give Putin military support.

Nato’s determined response, and the underperformance of the bogged down Russian army, may serve as a warning to Chinese president Xi Jinping and scramble his calculus for an assault on Taiwan. Larry Diamond, a senior fellow at the Hoover Institution thinktank in Palo Alto, California, told reporters this week: “Xi is pissed as hell because it completely changes the timeline and the dynamics of the situation.

“The most fascinating dimension of this crisis right now is to watch Xi Jinping be completely tied up in knots over what to do about this. He and the senior Chinese leadership are clearly struggling for a narrative and a response.”

Standing against a blue backdrop dotted with Nato logos, Biden addressed the issue of Chinese intervention at a press conference. He recalled that, in a recent call with Xi, he pointed out that many US and foreign corporations have left Russia. “I indicated that he would be putting himself in significant jeopardy. I think that China understands that its economic futures are much more closely tied to the west than it is to Russia. So I’m hopeful that he does not get engaged.”

He reiterated his message to Brussels that America is back. But towards the end of the question and answer session, someone raised European concerns that Trump might get re-elected in 2024 – raising the spectre of a return to the uncertainty, insults and Putin-praise singing.

The president replied: “One of the things I take some solace from is I don’t think you’ll find any European leader who thinks that I am not up to the job… I don’t criticise anybody for asking that question. But the next election, I’d be very fortunate if I had that same man running against me.”

Steeped in foreign policy after decades as a senator and vice-president, Biden is likely to be thinking about geopolitical questions in terms of decades. Unfortunately for him, his political legacy could be decided by Tucker Carlson and viewers’ demand for instant gratification.