In the mid-90s an American nurse, Greg Mortenson, was sleeping in his car to save rent so he could fulfil a promise he made to build a school in remote northern Pakistan. Fifteen years later, his book of his epic journey, Three Cups of Tea, has been in the US bestseller list for more than four years; thousands attend his speaker events; he has raised millions for his charity, and built hundreds of schools in the Gilgit-Baltistan region. His book was top of the reading list for US troops deploying to Afghanistan.

It was an extraordinary story – until this week, when it was dismantled in the US programme 60 Minutes and in an ebook by one of Mortenson's former supporters, Jon Krakauer. Mortenson has admitted to "some omissions and compressions" while largely defending his work. But his myth has fallen apart with such astonishing speed that every- one is left wondering how on earth it persisted for so long.

Mortenson's feet of clay expose far more than one fantasist: they also reveal a lot about the naivety of Americans concerning the world and their role in it. No one questioned him too closely, and, more importantly, no one listened closely enough to what the Pakistanis themselves had to say: the unravelling of the Mortenson fable has come as no surprise there. Even in such a highly connected world, some forms of information still don't travel and certainly make no headway against the word of an American hero. Americans swallowed his tale because they wanted to. What empires – particularly those involved in violent conflict – need, above all, is heroes.

Making Mortenson a credible hero means traducing the whole region of Gilgit-Baltistan which, in his script, becomes a wild region of extremist Islamism drawn to violent terrorism. Time and again, he braves personal danger to follow his dream. His big pitch for the last 15 years is that schooling will divert potential terrorists: a "one-man peace mission" in the war on terror. By this account, the insurgency in Afghanistan/Pakistan is not political opposition to foreign intervention but a form of false consciousness inculcated in the madrassas. Get to the child early enough and they will grow up good democrats. It's ludicrously naive given that all the 9/11 bombers were highly educated.

Even more importantly, it has no relevance in Gilgit-Baltistan, which is a peaceful, predominantly Ismaili region whose inhabitants see the Paris-based Aga Khan as their spiritual leader. There is a strong Tibetan Buddhist influence.

Rather than Mortenson waging a lonely battle against ignorance, the Aga Khan Development Network has been building hundreds of schools in the region and has a track record of staffing them and keeping them open. As the Pakistani journalist, Rina Saeed Khan, points out, Gilgit-Baltistan has one of the highest literacy rates in Pakistan. She asks, quite rightly, why Mortenson didn't join forces with the network given their experience and expertise, instead of struggling desperately to work it all out for himself.

But an American putting money into a foreign-sounding aid foundation doesn't quite have the same marketing appeal as the "one-man mission" line that captures perfectly the boom in DIY aid: a new wave of fledgling agencies driven by individuals frustrated and impatient with bureaucracies and politics, who launch their bid to "make a difference". A myth which turns development into an amateur's hobby.

To every age, their own type of hero: the British empire had Gordon of Khartoum in the 1880s, and the Americans have Mortenson. He is the gentle giant of a man who stumbles into exotic and dangerous locations of which he knows little, and makes friends. This is the innocent abroad – an image of America in the world that is also evident in Mortenson's rival in the New York Times bestseller lists in the last few years, Elizabeth Gilbert's Eat, Pray, Love.

These hugely popular tales portray a deeply consoling myth of how the US engages with the world as these adventurous individuals wander through foreign climes, and in their expansive, endearing way want only to bring as much delight in their interactions with the locals as they experience themselves. Both books share the personal crisis/failure which is resolved by finding a new self (through a new sense of meaning or love) abroad: in both, the individual's emotional quest is the starting point and provides the narrative thread. These are knowable characters who effectively explain the exotic to home audiences. They offer homely, charming myths for an empire currently embroiled in deadly protracted wars, rather as Rudyard Kipling's fables delighted a previous age of imperialists.

But perhaps the most intriguing – and most serious – aspect of the Mortenson myth is that his "one-man mission to bring peace" is a continuation of a western drive to "civilise" the world. His parents were Lutheran missionaries in Tanzania. Mortenson describes grinding poverty and ancient tribal customs: it's a patronising form of orientalism.

Above all, Mortenson has talked about women's empowerment and his pledge to get girls into schools. Women need liberating from the oppressive tribal patriarchy. There is nothing original here – US foreign policy is now stuffed with the rhetoric of women's rights – but Mortenson has helped popularise one of the most astonishing conundrums: feminism has been co-opted as a rationale for the US war on terror. It dangerously justifies and confirms an American self-righteousness in central Asia.