British exceptionalism – the myth that Britain is uniquely different to its European neighbours – afflicts everything from our understanding of our place in the world to our domestic political situation. The rise of Scottish nationalism, the rightwing populist surge, Brexit, Corbynism: all are seen through the confines of the UK’s borders. And so it goes for Labour’s catastrophic electoral rout. But it does not detract from the party’s own failure to understand the broader context: across the continent and even the world, social democracy and the so-called political centre are in crisis.

When Jeremy Corbyn’s Labour won 40% of the vote in June 2017, and yet still failed to secure victory, it was nevertheless bettering almost all of its European sister parties. When Martin Schulz became leader of Germany’s Social Democrats in March 2017, Corbyn’s critics extolled him as an example Labour should follow. Six months later, Schulz took the SPD to its worst postwar showing – a calamitous 20.5% – and its polling has since declined further.

The French Socialist party took both presidency and legislature in 2012; it won less than 6.4% and 7.5% in each respective vote five years later. Italy’s Democrats scraped well under a quarter of the vote in 2018, and now only finds itself in power in a bizarre and profoundly unstable coalition with the populist Five Star Movement.

The late 1990s were the high point of third way social democracy, when Tony Blair, Lionel Jospin and Gerhard Schröder were Europe’s preeminent politicians: two decades later, and their parties are in existential crisis.

Austria’s Social Democrats have topped the poll in nearly two-thirds of the country’s postwar elections, amassing more than half the vote 40 years ago. This year, they collapsed to barely over a fifth of the vote: Austria’s Greens have now formed a governing pact with the right, agreeing to anti-migrant laws, banning the headscarf in schools and enacting tax cuts in exchange for some environmentally friendly policies.

‘A new progressive government beckons in Spain thanks to a coalition between the socialists and the radical left Podemos.’ Podemo’s leader, Pablo Iglesias, and acting Spanish prime minister, Pedro Sánchez, sign preliminary policy agreement on 30 December. Photograph: JuanJo Martin/EPA

The Dutch Labour party were runners-up with nearly a quarter of the vote eight years ago: in the last election, they came seventh with a dire 5.7%. Greece’s social democratic Pasok gave its name to “Pasokification” – the process in which a centre-left party implodes – and for good reason: it went from 43.9% of the vote in 2009 to a mere 4.7% five years ago, and has never recovered.

Beyond the confines of western Europe, there are few glimmers of hope. Both Hungary and Poland are ruled by rightwing and authoritarian regimes in which centre-left forces are utterly marginalised. While Hillary Clinton’s supporters cling on to her triumph in the popular vote, Donald Trump was supposed to suffer the landslide drubbing endured by the hard-right populist Barry Goldwater in 1964, not win the electoral college. In Brazil, a centre-left candidate was defeated by the far right – aided and abetted by the outrageous incarceration of popular leftist Lula da Silva. Meanwhile, India’s rightwing extremists, in the form of the BJP, have battered the once dominant centre-left secularists of the Congress party.

Other than a promising revival in Nordic countries, it is the Iberian peninsula that offers hope, and here the lessons are instructive. Portugal’s Socialist party came second on an uninspiring manifesto in 2015, but formed a pact with radical parties and shifted leftwards. The new policies proved so popular that their vote surged in last year’s election, and most Portuguese voters opted for the left. A new progressive government beckons in Spain thanks to a coalition between the socialists – who have been dragged to a more progressive position – and the radical left Podemos, committing to measures such as tax hikes on big business and the rich, improved workers’ rights, a hiked minimum wage and radical climate policies.

In an age of rightwing populism and a culture war partly triggered by the way globalisation has fragmented senses of belonging and identity, both centre-left and radical left should have the humility to accept that neither currently have the answers. Those assailing the Labour left for December’s disaster would have a stronger position if they could point to thriving success stories abroad.

Their default answer tends to be France’s Emmanuel Macron, who belongs to no shade of the left, is enforcing regressive policies which benefit the rich, and who only won by defeating a hard-right candidate in the second round of a presidential election in which polls showed any other candidate would also have triumphed, including the radical left.

In multiple countries, divides have opened up between a disproportionately older demographic with capital and socially conservative views, and disproportionately younger voters with progressive social values who are blighted by economic insecurity. Building a winning coalition from either a centre-left or more radical position in this political age is an immense challenge, one in which there are few clear answers.

If the Labour leadership contest is not simply to prove another crisis-stricken chapter in the party’s history of turmoil, then this is where the debate must surely focus.

• Owen Jones is a Guardian columnist