Double Booker winner Peter Carey was always unimpressed by the decision to open the prize up to American authors. "I find it unimaginable that the Pulitzer or the National Book award would ever open their prizes up to Britons and Australians," he says. The "old Booker" had a "particular cultural flavour", he adds. "I think there was, and there is, a real Commonwealth culture. It's different. America doesn't really feel to be a part of that." As for this year's America-expanded award, Carey was rooting for the eventual winner, and fellow Australian, Richard Flanagan's The Narrow Road to the Deep North – "a serious guy who can really write".

When I meet Carey in Faber's London offices the 71-year-old is fizzing with energy and puckish good humour. He has flown in from his home in New York ahead of the publication of his new novel Amnesia at the end of the month. His 13th major work of fiction, it is perhaps his most overtly political – loosely, though not literally, inspired by Julian Assange, cyber-activism and the dark world of American state surveillance. It is the story of WikiLeaks as if transmogrified by Dickens and turned into a thrilling fable for our post-Edward Snowden era.

The novel's title refers to Australia's forgotten role as a US client state. Its narrator Felix Moore is a seedy radical writer – known to himself as "Australia's last serving leftwing journalist". Felix is profoundly unreliable; a lousy husband and father, broke, and a dodgy storyteller, too. His job is to write the biography of Gaby Baillieux, the most wanted woman on the planet. Gaby is an elusive female hacker. Her computer worm virus has magically sprung open the doors of Australia's and America's prisons. Moore's patron, meanwhile, is a Murdochian property baron, Woody Townes, who may or may not be the journalist's mate. The plot rapidly shoots off in dark directions.

How closely, I wonder, do Carey's own views align with those of Felix Moore? Much of Amnesia deals with two murky historical events: one is the battle of Brisbane in 1942, when Australian and American servicemen fought each other on the city's streets; the other is the constitutional crisis of 1975, when the British governor general dismissed prime minister Gough Whitlam and his progressive cabinet. In Moore's view – and Carey's – this was, unambiguously, a CIA coup.

"There is no question that the US government of 1975 didn't wish to have the government we'd elected," Carey says. He thinks that what did for Whitlam was his threat to terminate the lease on Pine Gap, a top-secret US spying facility near Alice Springs. Days later Whitlam was out. "He was a smart man. But I don't think he really knew what he was messing with," Carey suggests. Whitlam's CIA-engineered overthrow was the same as Salvador Allende's in Chile in 1973, minus the bloodshed, he says.

For "emotional" reasons, Australians are unwilling to recognise this illegal removal or their satellite status, Carey argues. "We have always been a client state. Our situation is really to be a colony". First a colony of England and then, after the second world war, of the US, whose navy rescued Australia from Japan. "I grew up with my mother saying: 'The Japanese were coming to kill my lovely baby. The Americans came and saved us.'" The baby being Carey? "Yes, hard to imagine," he grins.

Fast forward, and the first international figure to spill American secrets on a grand scale is an upstart Australian. In 2010 Assange presided over a series of stunning leaks. He released warlogs from Afghanistan and Iraq, and secret US diplomatic cables. There were a quarter of a million of them. WikiLeaks' disclosures sparked uproar and angry US accusations that Assange was a "traitor". This, Carey notes, was ridiculous. "I'm reading the US press and they are saying Julian Assange is a traitor and I'm thinking: 'Excuse me. This is a citizen of Australia and you know sweet fuck all about him.'"

America's inability to understand Assange was symptomatic of a wider malaise, Carey feels. "The failure of the US's foreign adventures often seems to have its roots in the US's total ignorance of things on the ground, of the countries that they fiddle with. It wouldn't even occur to them that Assange was Australian, that they had fucked over Australia and now Australia was fucking them over." He says he's speaking as an "individual with passions" not as a "deep political thinker".

In 2011 Carey was having lunch in New York with Sonny Mehta, his long-term US publisher. They talked about Assange – why Assange's Australian-ness mattered to Carey, and how he felt a connection to an Australian with a hippie activist mother and an accent that – to Carey's ear – sounded "something like north Queensland". At the time Assange had signed a deal to write his autobiography. It was expected to be a global publishing sensation. The only thing missing was a ghost writer. Mehta asked Carey if he wanted the job.

"My answer was no." Carey stresses that this was never a "serious" offer. No other agents were involved. "We both knew it was one of those ideas that was like a cloud of smoke. One, I'm an appalling journalist. I would be the worst person on earth to be called to write an account of someone else's life. Secondly, as a fiction writer you're in control. You kill people and change people, and change the words in their mouths all the time. If you are the subject of a memoir or biography like that people continually squirm on the hook. They want to be in control. It's the nature of the victim to want to control, and sometimes falsely to believe they can control."

The job of ghost fell to Andrew O'Hagan – a "fabulous writer", says Carey. But the ensuing project was a disaster. Assange fell out with his publisher and then disowned his own memoir. Carey hasn't met Assange, who is still holed up in the Ecuadorian embassy, a 15-minute taxi-ride from Faber's HQ. (Carey has been with the publisher since 1980 for his first story collection, The Fat Man in History.)

"Whether one likes Assange or not, the fact remains that there have been these three individuals who in different ways have changed the history of our time. Edward Snowden is one, Bradley Manning another, and Assange one more," Carey says. He describes Snowden as "an exceptionally courageous man". "I was just thrilled that someone was making the reality of our lives known to us. The only thing that surprised me about Snowden is that I automatically assumed he was of the left." In fact Snowden – or at least the early Snowden of the chatrooms – is a conservative and a fan of Ron Paul's.

In 2013 Snowden revealed that the US National Security Agency (NSA) engages in mass global electronic surveillance. Australia's own spies are complicit. (Carey's character Felix Moore dubs Australia's home-grown spooks "the CIA's great bum boys"). Was any of this a surprise? "No, no. I was one of the people who has been called a leftwing conspiracy theorist. I've always thought: 'Why wouldn't it be like that.' One of the things that Snowden did by just existing was to make the ideas in this book credible. Of course there are conspiracies. They [the spy agencies] have car parks full of people whose job it is to do these things."

The NSA revelations happened when Carey was halfway through writing Amnesia. Early on he decided that his hacker character would be a woman – more of a challenge, and more interesting, he says, than delineating her "farting, pimply" male cousins. The novel deftly captures computer culture: there are slabs of code; lines from Zork, an early text-based fantasy game; references to the Mac IIx. Carey recruited a friend from Google and a professor of artificial intelligence at Manhattan's Hunter College – where Carey teaches creative writing – to make sure he'd got it right.

But it is non-techie Moore who is Amnesia's peccant hero. He strikes me as the latest in a line of hard-pressed writers who thread their way through some of Carey's fantastical fiction. (Others might include Tobias Oates in Jack Maggs, Carey's reworking of Great Expectations, or the Australian outlaw Ned Kelly, whom Carey ventriloquises in his 2001 Booker winner True History of the Kelly Gang.) "I'm someone who always wants to do everything differently," he says. "If I have a pattern I'd rather I didn't have a pattern. I want every book to be unpredictable and new. Damn it!"

The novel also marks a return by Carey to imaginary Australia. Many of the locations – the bohemian Melbourne suburb of Carlton in the 1970s, for example – are written with forensic precision. Carey plunders some things from his CV: he was born in Bacchus March, Victoria, the son of a car dealer, and studied science at Melbourne's Monash University, all of which pop up in Moore's story. Carey says he also researched "to a lunatic degree". The result is "an Australia – maybe not the Australia of now" in which the writer says he feels "vividly alive".

While reading Amnesia I found myself sometimes turning to Wikipedia for a bit of assistance. Australian fauna and flora are done in glorious technicolour: kookaburras, butcherbirds, killer magpies. I wasn't sure, though, what an angophora was (ghost gum tree, grey bark) or a melaleucas, or wattles, or wild lantana. Minor Australian painters left me stumped. Carey makes few concessions to non-Australians. Is this deliberate, I ask him. Or even political?

"I suppose my answer is the perfect chippy antipodean response: they [American writers] don't really make a lot of concessions to us," he says. "I'm not really thinking that Tom Pynchon's going to worry about whether he is understood by Australians."

Carey recalls that 20 years ago many Australian authors, at the behest of US publishers, would change spellings and add US-friendly explanations. "I've never worked like that," he says. "My publishers have never wanted me to. British publishers were never like that." He adds: "If you're a curious reader you'll find out. After all, we grew up reading Flaubert in translation. That wasn't written with us in mind."

He has lived in New York since the early 1990s. "I like its energy. I love it as a walking city. I don't drive. I don't have a car any more. I can cross universes in an hour just walking on the street." As he tells it, he is very much an accidental emigre. "The basic supposition is if an artist moves from one country to another, that involves a rejection of the first country and a protest against it, and a commitment and a love of a country that one goes to. In fact, the way it worked in my particular equation was that I fell in love with a woman who desperately wanted to direct theatre in New York."

This was Alison Summers. The couple had two children; they divorced after nearly two decades together. Carey remarried and lives in a SoHo apartment with his British publisher wife, Frances Coady. He has dual American and Australian citizenship; Britishness seeps in via BBC Radio 4 dramas, of which Coady is fond. He says he voted for Obama in 2008, and "wept when he was elected". Obama is a "terrible" let-down, though. He worries about American democracy.

His 14th novel, on which he is already working, is again set in Australia. The book "deals with matters Australian that have been important to me my entire life and that I never thought I would be able to write about". Given what we now know about US snooping, does he take steps to shield his manuscript and emails? Or use an Olivetti typewriter, like Moore? No, he says, he doesn't. Nor does he bother with encryption. "I fully expect that anyone who wants to read my email will read my email, look at my bank account and do whatever they want."

That doesn't mean Carey thinks this is acceptable. "Privacy should be a fundamental human right," he says. "We've been tricked out of it to a great degree by giving up little bits of it along the way, because it's easier to give some information to Amazon or to Walmart or to whatever it is. So the water is getting hotter and hotter. We are used to being in the warm bath. We are putting up with it. But it is sort of evil, I guess." He adds: "We should be able to keep our information, our conversations private."

After the era of "George Bush and those criminals", in Carey's words, we have ended up in a place where the state helps itself to our private data. Things are worse than most of us realise, he believes. "It's more nightmarish than we can normally really allow ourselves to see. It's like amnesia in that sense: that you can't afford to see what you have done or where you are. Because if you did, you would be in deep despair."