The withering complexity of a four-year-old global financial crisis — in the euro zone, United States or increasingly in China and across the faster-growing developing world — is now stretching the minds and patience of even the most clued-in experts and commentators. Unsurprisingly, the average householder is perplexed, increasingly anxious and keen on a simpler narrative they can rally around or rail against. It’s fast becoming a fertile environment for half-baked conspiracy theories, apocalypse preaching and no little political opportunism. And, as ever, a tempting electoral ploy is to convince the public there’s some magic national solution to problems way beyond borders.

For a populace fearful of seemingly inextricable connections to a wider world they can’t control, it’s not difficult to see the lure of petty nationalism, protectionism and isolationism. Just witness national debates on the crisis in Britain, Germany, Greece or Ireland and they are all starting to tilt toward some idea that everyone may be better off on their own — outside a flawed single currency in the case of Germany, Greece and Ireland and even outside the European Union in the case of some lobby groups in Britain. But it’s not just a debate about a European future, the U.S.  Senate next week plans to vote on legisation to crack down on Chinese trade due to currency pegging despite the interdependency of the two economies.  And there’s no shortage of voices saying China should somehow stand aloof from the Western financial crisis, even though its spectacular economic ascent over the past decade was gained largely on the back of U.S. and European demand.

Despite all the nationalist rumbling, the crisis illustrates one thing pretty clearly – the world is massively integrated and interdependent in a way never seen before in history. And globalised trade and finance drove much of that over the past 20 years. However desireable you may think it is in the long run, unwinding that now could well be catastrophic. A financial crisis in one small part of the globe will now quickly affect another through a blizzard of systematic banking and cross-border trade links systemic links.

Just take the euro zone for a start. HSBC economists on Friday said the costs of a euro zone breakup would be “a disaster, threatening another Great Depression” and far outweighed the costs of repairing the flawed fiscal backstops to the monetary union — especially given the wealthier creditor countries within the union tend to ignore the benefits they’ve reaped from the euro over the past 12 years. Aided by the “entangling effects” of the euro, it showing that cross-border holdings of capital have exploded from about 20% of world GDP in 1980 to stand at more than 100% now (global GDP was estimated by the IMF to be about $62 trillion last year). By contrast, the first wave of globalisation in the late 19th and early 20th century saw cross-border holdings peak at 20% of world GDP before WW1 reversed everything.

“A euro break-up would be a disaster, threatening another Great Depression,” wrote HSBC chief economist Stephen King and economist Janet Henry. ” Cross-border holdings of assets and liabilities within the eurozone have risen dramatically, leading to a tangled web of mutual financial dependency. With the re-introduction of national currencies, disentanglement would proceed at a rate of knots, undermining financial systems, generating massive currency moves, threatening hyper-inflation in the periphery and triggering economic collapse in the core.”