Opinion: in the aftermath of the EU referendum, Britain has a once-in-a-generation opportunity to redesign itself as a coherent, relevant and functioning nation for the 21st century, says Sam Jacob.

You know that feeling when you break something? When that thing, which you didn't even need to think about when it ran smoothly, is now in pieces? Well, that was the expression on the face of the Leavers on the morning after Brexit. It's bad enough with, say, a toaster. But this is different – it's a nation that's in pieces.

But sometimes its only when things break that you find out how they work.

The idea of nationhood was at the heart of the referendum. All those words – sovereignty, democracy, control – appear to have solid meaning when we look them up in a dictionary, but collapse in on themselves when they come into contact with the modern world.

What do these concepts mean? What is sovereignty? What is democracy? Most of all, what actually is a nation?

On one hand we have the traditional idea of a sovereign nation, and on the other a modern supra-national idea of state. The tension between these two ideas has been building for decades.

In 1993, the then prime minister John Major gave his now-infamous speech about "long shadows on county grounds, warm beer, invincible green suburbs, dog lovers and pools fillers". We laughed. But looking back, it was a deep and intelligent plea.

His argument was that you could be both a nation and part of a pan-national movement simultaneously. That the EU as a supra-national entity would provide the necessary shelter for us to cycle on country roads, drink beer the way we like it, look after our dogs, and read Shakespeare – Britain "unamendable in all essentials".

Instead the tension that his speech had hoped to suppress only ratcheted tighter until the entire modern settlement fractured into pieces.

But we should never, as Churchill once said, let a serious crisis go to waste. We have to seize this opportunity to try to figure how we can put a coherent, relevant and functioning idea of nation back together for the 21st century.

This means confronting the tension that is at the root of political strife all around the world – the strain between how the world works (in broad terms globalisation), and how we think of ourselves as individuals (call that identity) and collectively (as nation). And we need to find new ways of brokering settlements of public good within the seemingly inescapable framework of late capitalism.

Given the fundamental questions of organisation, function, threshold and spatial organisation, we could imagine nationhood as a design project or as architecture at its fullest expression – where the usual relationship of architecture serving society is reversed, and we use the tools of design to construct possibilities of society.

Indeed the very word statecraft – the thing that Britain's going to need heaped spoons of in the near future – suggests that "state" is a thing that is fabricated rather than an inert inevitability, a thing that needs to be made and a thing that has to be designed.

The history of nationhood shows that our idea of what a state is is far from a natural, inevitable thing. Our modern idea of nation really only emerges in the late 18th century, with the French and American revolutions.

The effects of industrialisation reshaped the old agrarian order into something resembling a modern state. Empire too influenced the idea of state cementing the idea of government, in order to exert control and organisation over colonies.

And it was around these ideas that new myths of nation emerged – the American Dream, the German Sonderweg, the idea of French-ness. These national mythomoteurs combined pragmatism with mythological narratives.

The EU, emerging out of WWII, was consciously wary of the dangers of myth. Hence its propensity to pragmatic bureaucracy, shorn of the traditional symbols and stories that swirl around older ideas of nation.

This though was (is) also its weakness – one that OMA's projects for the EU tried to address though articulating narratives of post national European-ness. For example, in the barcode flag where an op-art graphic intensity attempted to create a form of collective contemporary pageantry. This retroactive effort came far too late to galvanise any sort of sentimental attachment to EU membership – at least in the UK.

The fact that we've voted out, with no manifesto for what out actually means, is a once-in-a-generation opportunity to confront the problem of nation. We need to find a viable 21st century concept of nationhood that is not organised around 18th and 19th century ideas and problems, but in the context of a networked world.

Nowhere is this issue more volatile than in the idea of the border. From the colour of the passport to immigration policy, the edge is the place where – both literally and conceptually – our national ideals comes into contact with the rest of the world.

What is a border in the 21st century? How could a threshold of nation operate in an age of electronic communication? When the local is intimately connected with the global? When the complexities of trade are both hand-to-mouth and subject to international logistics? Where our desire for authenticity is fuelled by its apparent erosion by globalisation? When the flutter of butterfly wings can cause all kinds of typhoons on the other side of the world?

For an island nation like Great Britain, the idea of the edge as defining characteristic is only exacerbated.

Britain's problem is that it can't ever forget it's an island, a mentality ironically captured in the St George Britpop-era ad for Blackcurrant Tango, which ends with a gathering hoard of flag-waving Englanders, a boxing ring and a Harrier Jump Jet massed atop the White Cliffs of Dover railing against hair gel and Europe. It was funny in the 1990s. But in our more complicated and troubling times farce seems to be repeated as fact.

Britain's own national myths present themselves as apparently eternal. We have no cultural memory of founding, no invasion (since 1066 at least), and no defeat.

This sentiment of natural-ness in our national identity is so strong that it trumps any need for anything as official as a constitution. When we have nature itself on our side, who needs bureaucracy. Compare this, say, to the hallowed status of the Constitution in the US, a document not without continuing controversy, but one with the significance of a religious relic.

Geography acts as our de-facto constitution. Which is why landscape is so fundamental to British culture, why the Picturesque is perhaps our greatest cultural invention, why the gardens of Stowe and Stourhead are so significant, why landscape painting has dominated visual culture so strongly, why landscape has figured so prominently in our literature, and why gardening is our traditional national pastime. To rephrase that Shakespearian cliche, it is not character that is our destiny, but geography.

But our geographic imagination – as the Picturesque should tell us – is far from natural. Instead its a terraformed, synthetic version of nature. One even more convincing than nature itself.

What it should also tell us is that nation is already an architectural project: a spatial, aesthetic, environmental, organisational construct. One where edges, boundaries and thresholds are of key significance.

Every night we watch the weather. Every night we see the clearly defined figure of the British Isles – 7,723 miles of coastline that create a shape as strong as any of the other national symbols of Union (the flag), Crown (the crown, obviously) or State (the Houses of Parliament for example, or the glossy black door to No 10).

But the simple unarguable idea of nation suggested by the map is contradicted by the reality of the territory. This has a far more complex, bloody, fluid and unresolved nature.

The British Isles, Great Britain, the United Kingdom: principalities and nations jiggle around in a competing set of identities even while the figure describes itself so clearly. Nation is both high-definition and out of focus. Form without clear content.

Compositionally too, the map is laden with aesthetic meaning. There's that little island just off the left hand shoulder of continental Europe, small yet jaunty on the map, full of graphic character.

Does the map – a thing that essentially claims to describe things objectively – accidentally create other kinds of meaning? When we watch the weather forecast, are we also imbibing graphic meanings that might more obviously be associated with the abstract composition of a Constructivist painting? Does the map change the meaning of the place that it describes?

Look instead at how a Venn Diagram describes national relationships within the British Isles and you see an entirely different graphic effect, one that prioritises conceptual relationships over physical boundaries.

The idea of an island itself is of course important. It suggests isolation. It's the kind of place you bury your treasure if you are either a pirate or an offshore banker. It can be an idea of utopia (Moore's original Utopia had to be an island of course), or somewhere special as in "this sceptred isle". But is also a place where things get out of hand (Lord of the Flies) or weird (Dr Moreau).

It can't be by chance that these all the projections of the possibility of an island all emerge from the British imagination. Again and again literature has provided us with a space to think through the physiological problem of our geographical fate.

The project of constructing a new idea of nation could, if taken seriously, be a profound moment in the continuing story of Britain, its own internal union and its relationship to the wider world. This new definition of nation could and should be as fundamentally radical as any of those previous ways of structuring a nation around industry or empire.

To create this vision though, we need more than hastily convened Whitehall departments, aggressive headhunting of experienced trade-deal technocrats or armies of lawyers to go through 40 years of intertwined legislation.

We need a vision of nationhood that mobilises our own heritage in its fullest, fiercest form to face a contemporary world. A vision that leans of the imagination of novelists and poets who have wrestled with the idea of nationhood. One that draws on the ways designers have imagined space, the organisation of landscape and the possibilities of threshold, that learns from the artists who have framed landscape into forceful cultural ideas that resonate deeply.

Because to make the best of this mess we're in we should remember that the idea of nationhood is not written by the land. We shaped the land before it shaped us.