Steve Bannon is on a mission. President Trump’s former chief strategist has visited Europe twice in the past four months, touring several capitals. He has been spreading the gospel of the “national populist revolt”, and he sees Europe as fertile ground for his global crusade. Maybe there is some truth in that. Italy’s current politics are a gift to him. But he has also been applauded by audiences in Prague, Budapest and France. Have we been paying enough attention?

It’s easy to dismiss Bannon as an isolated maverick, a man who was chucked out of the White House last August before being fired by Breitbart in January. It’s also tempting to see his activities as being mainly aimed at the Anglosphere: reaching out to US audiences and Brexiteers, rather than to the old continent. It’s even possible that he is trying to grab the attention of one man and one man only: Donald Trump – to get back into his good graces.

But I don’t buy the half-reassuring line that says Bannon has set his sights on Europe simply to compensate for his supposed estrangement from Trump. His trips across the Atlantic are part of an ideological struggle between “nationalists” and “globalists”, a battle that he is seeking both to frame and to escalate. He has obviously been using his White House pedigree to open doors here: the like-minded will flock, and others believe that his presence might offer insight into, if not access to, Trump’s circle.

What’s clear is that Bannon has been busy nurturing relationships with some of the most disruptive forces in Europe. And he was interested in the continent long before Trump launched his bid for power. Remember that in 2014 Bannon chose a Vatican palace as the venue to set out his worldview, before an audience composed of ultra-conservative Catholic groups. In Budapest he was recently introduced on stage as “a great thinker”. In Italy he hailed the new far-right populist coalition as a “historic alliance”. In Prague he called the postwar liberal order a “fetish”. Earlier this year, in northern France, he attended a gathering around Marine Le Pen, where he electrified the crowd with these words: “Let them call you racist, xenophobes, nativists, homophobes, misogynists – wear it as a badge of honour!”

Donald Trump in Poland last year, when he said the ‘fundamental question of our time is whether the west has the will to survive’. Photograph: East News/Rex/Shutterstock

So what is Bannon’s plan? Who’s financing him? How might his activities play into next year’s European parliament elections? Most journalists who have met him in Europe focus on Trump or US politics. That leaves aside the scope of his brand of “alt-right” transatlanticism. Is he just an opportunist seeking the limelight wherever populists win? Or could Bannon be the advance guard of a Trumpian onslaught against the European project itself?

Trump’s hostility to the EU is hardly a secret. We know he has no idea what the European project is fundamentally about. His policies leave little doubt that he wouldn’t care if it disintegrated altogether. It’s interesting that Bannon’s travels to Europe coincide with a brewing transatlantic trade war, the ticking clock of Brexit, and the struggling efforts of EU leaders to stave off another eurozone crisis.

In fact, we’d be fools to think Bannon is just an attention-seeking clown. He’s far from stupid. And he’s worth listening to, as a means of understanding how what has bound the US and Europe since 1945 is unravelling. While in Europe, he said Trump’s 2017 Warsaw speech – in which the president declared that the “fundamental question of our time is whether the west has the will to survive” – was “the most important of his presidency”. Think about it. That speech contained nothing less than a redefinition of the west as a nationalist, Christian entity pitted against barbarians.

Bannon doesn’t expressly call for the demise of the European project. Rather, he expects it to mutate, following the dismantling of its single currency and the defeat of liberal and universalist values, into “a confederation of free and independent states”. Because populists started making gains in Europe earlier than in the US after the financial crisis, Bannon believes it is one step aheadn politics. He has spoken of a “brave new world” starting in Europe.

He says Europe needs to worry about 'the new axis of China, Turkey and Persia against the judeo-Christian world'

Last week, shortly after Bannon’s latest European tour, I met Poland’s secretary of state for European affairs, Konrad Szymański, on the sidelines of a conference in Tallinn. Szymański, whose national conservative government rolled out the red carpet for Trump last year, didn’t want to say much about Bannon. But he did insist on the need for Europe to reconnect with “1950s-1960s traditions” and “a more communitarian sense of national identity”. Bannon’s Gramsci-style culture war against “elites”, and his exhortations to be “very aggressive about confronting Brussels”, have an eager potential audience in Europe, not least in its central and eastern regions.

Perhaps the influence one man wields shouldn’t be exaggerated. But Bannon did, after all, help get Trump elected, and now it looks like he’s laying the groundwork for the emergence of a kind of “alt-right International”. He’s working to undermine European liberal democracies in the name of an insurgent ideology that blends ultra-nationalism, the defence of “workers’ rights”, and protectionist reflexes. In Europe he behaves almost as a spokesman for Trump. He says Europe needs to worry less about Russia, and more about “the new axis of China, Turkey and Persia against the judeo-Christian world”.

Bannon and his European allies embody everything Emmanuel Macron – Europe’s liberal flag-bearer – recently warned against when he spoke of the danger of a political “civil war” within the EU. The title of Bannon’s talk in Budapest was “Trump’s America First and its impact on central Europe”. He may come across as an eccentric, a rabble-rouser, even an entertainer. We should be tracking his tactics and his moves, not just his wisecracks. Otherwise we risk sleepwalking to disaster.

• Natalie Nougayrède is a Guardian staff columnist