It is perhaps western Europe's most divided nation, a country so riven that it once took 541 days to form a government.

But for the past three weeks Belgium has had a very different feel. Three weeks of cheering their World Cup heroes, waving flags and chugging beers together have shown querulous French and Flemish speakers that perhaps they can live together after all. Years of sniping between the country's fractious communities seem forgotten in the euphoria of the football as Belgians reveal a character trait unseen for a generation: belief in themselves.

That is certainly the impression in Good Kompany, the bar on Brussels' Grand Place owned by the Belgian captain Vincent Kompany, which has been heaving with crowds on Belgium's match nights. "It has been incredible. It really has brought the country together," says Jesse de Peter, Good Kompany's general manager. "In here, the fans chant alternately in French and Flemish, which is almost unheard of."

The excitement has grown as Belgium has progressed in the World Cup, their first since 2002. Dutch and French language broadcasters boasted record viewing figures for the exhilarating second round victory over the US on Tuesday, even though the game dragged on well after midnight.

Across the country, town squares have been packed with raucous, red-clad crowds watching the games on big screens and celebrating long afterwards. And a parade through Brussels' boulevards is planned for the team whatever the result in Saturday's quarter-final against Argentina.

For Belgian foreign minister Didier Reynders, the World Cup is reviving a spirit that has been dormant for too long. "It is showing people that Belgians can achieve great things together," he told The Guardian. "We see it amongst the players themselves: all but two of the 23 in the team play abroad and they see the arguments between Belgium's communities differently."

However, Reynders, from the liberal Francophone Movement Réformateur (MR) party, is cautious not to draw too many conclusions. "We shouldn't exaggerate the effect: our country's future does not depend on the game against Argentina," he says, noting that the previous high point of Belgian football – losing the 1986 World Cup semi-finals to Diego Maradona's Argentina – did not translate into political stability: the government fell the following year.

Belgium is still in an uncertain political state. Last month, the Flemish nationalist N-VA, which wants to dissolve the country, won its highest ever share of the vote in national elections, nudging Belgium closer towards Czechoslovakian-style divorce. Negotiations are ongoing to form a new coalition, though in Belgium this can literally take years.

Johan Vande Lanotte, the economy minister and deputy prime minister notes that even N-VA voters have been cheering for the Red Devils. "We can vote one week for a party that wants to split the country, and another week we can wave the Belgian flag for the football team," he says. "Yes, it is strange, but then we were the inventors of surrealism."

While Lanotte, a Flemish socialist, doubts it will shift the current political dynamic, he says the football has nonetheless already changed attitudes in one significant area: change how Belgians see minorities. Many of the Red Devils have mixed backgrounds, including Kompany, whose father was a Congolese immigrant; Marouane Fellaini, whose parents were from Morocco; and Adnan Januzaj, who has Kosovan-Albanian parentage. "We have a real diversity in the Belgian team, and that has clearly been accepted," Lanotte says.

For Dave Sinardet, a political professor at the Free University of Brussels (VUB), the surge in Belgian pride shows how local and national identities shift according to events. "What is happening with the Red Devils is that the latent feelings are coming to the surface," he says.

And even if the immediate political effect is limited because elections have just taken place, Sinardet says it can change attitudes in the longer term. "In a context where politicians claim that we don't have anything in common, there is a broad political meaning," he says. "I see it having a positive effect, creating a more positive appraisal of what Belgium can be, and how the north and south can work together."

In the Grand Place in Brussels, most fans believe the effect will endure, if only because they expect Belgium to defy the odds and defeat Argentina tonight. "Of course we can win. We have shown we can play against anyone," says Yves, a student from Nivelles in Wallonia. Stefan, an IT consultant from Ghent agrees. "Argentina are a one-man team, built around Lionel Messi. But we have a real squad that works together," he says. Such sentiments have been all too rare for the Red Devils in recent years, rarer still for Belgium as a whole.