Huddled together in a cafe in Leigh on Friday, the Hartley-Walls looked like any other family enjoying lunch together at half-term. But it wasn't hard to work out that Philip, Kimberly and their 12-year-old daughter Kailey are not from anywhere near Greater Manchester.

"What's a butty?" asked Kimberly, a 40-year-old preschool teacher, as she puzzled over the menu, pronouncing the t's as if they were d's. "It's a saaaandwich," said Philip in the same broad California accent.

Philip was actually born up the road in Bury 42 years ago, but when he was nine his British parents upped sticks to Los Angeles and never returned, bringing up their four sons as all-American boys.

Philip says he never particularly wanted to make the 5,700-mile trip to the land of his birth. Like many Americans, he never even bothered applying for a passport, having originally entered the US on his mother's.

He had a green card, giving him "permanent alien residency status". He had a driving licence and had built up a small tiling business, and claims to have paid taxes for years. "Despite being born in England, I do not feel remotely British. I've never thought of myself as being anything other than American," he said this week.

It was a dangerous assumption, as he found to his cost when a small slip-up on the US/Mexico border in May 2009 ended up with him stranded in the north-west of England, an alien once more.

It's a case which Andy Burnham, his local MP in Leigh, describes as "the most unique and troubling" he has encountered in his 12 years in parliament. So much so that he has taken the step of writing to Barack Obama and asking him for clemency.

On 21 November 2010, Philip landed at Heathrow airport carrying a rucksack and a pack of cigarettes. He had 32 cents (about 20p) in his pocket and no idea what to do next.

He only knew one person in the UK – a Mancunian he met at an immigration removal centre in Texas who was being packed back off home after his American marriage went sour.

The Mancunian had once offered to put Philip up if US immigration followed through on its threat to send him to the UK. Philip didn't know where Manchester was exactly, but decided that England was so tiny he could probably walk it.

He had barely left the terminal when a friendly policeman put him right, and he went to the airport chapel instead. There he met "two kind old ladies who believed my story". He told them that his wife and daughter were back in Arcadia, Los Angeles, where he had lived since 1981. However, because he had never actually gained US citizenship, he landed in hot water on a brief trip to Mexico when he mistakenly told an immigration officer on the way back that he was indeed from the land of the brave.

What followed was a punishment which, as Burnham argued in his letter to Obama, was "totally disproportionate to the original offence". Philip had originally been arrested on suspicion of drug and firearm offences after border police found drug paraphernalia and a disassembled gun in the back of the car in which he was a passenger. But he was eventually only charged with "making a false statement to a federal officer" – a felony – by wrongly claiming to be American.

He pleaded guilty and served seven months in a federal prison.

On his release date he expected to be sent home but instead claims he was handcuffed, shackled and chained to another prisoner and put on a bus to an immigration detention centre in Haskell, Texas. Under US law, any green card holder found guilty of a felony can be deported.

Months later, after a failed appeal, Philip was on a bus from Heathrow to Manchester, his ticket paid for by the kind ladies from the airport chapel. The family of his friend from the detention centre met him at the other end and, after treating him to fish and chips, took him back to their home in Tyldesley, 8.9 miles northwest of Manchester, where he lived for at least six weeks. "Proof," said Philip, "that there is goodness still left in this world."

He has been in the area ever since, barring an ill-advised and ill-fated attempt to regain entry to the US by changing his surname by deed poll (from Hartley to Wall, hence the new double-barrelled concoction) and getting a British passport.

Almost three years on, he is now living in Bolton, walking with a stick after a recent operation, wearing two hearing aids and taking strong anti-depressants. Still living on LA time, he rises at 3.30pm every afternoon to Skype Kimberly and Kailey, eight hours behind, before they go to work and school, and again when they return.

Last week the family were reunited for the first time in two years, visibly delighted to be back together. Kailey, who has learning difficulties which mean she has the body of a 12-year-old but the mental abilities of a six-year-old, clung to her father, telling him over and over again that she loved him.

"The separation has affected her a great deal," said Kimberly, who is using all of her annual leave and savings for the three-week trip. "She's had an emotional breakdown and has been in counselling at school because her behaviour has gotten so bad."

Back in Arcadia, Kimberly has had to sell the family home after being unable to keep up with the mortgage payments on one salary. On Burnham's advice, she has recruited three Californian senators to the family's cause, but so far, despite the family spending thousands of dollars on their fight, it has come to naught.

On Friday Burnham made a bold promise to the family: "We WILL get you back together, I promise," he said in Leigh town hall. "I don't know how long it takes, but we will do it."

He said to the Guardian: "This is a family that has absolutely nothing to do with here. They have been brought here, in my view, by the sheer intransigence of American bureaucracy. The rules are draconian and make no allowances for the right to a family life. I'm not anti-American, I'm just amazed that the American system hasn't been able to show some clemency or mercy at all."

As Burnham told Obama: "[He] may be guilty of an on-the-spot inaccurate statement, and a lack of knowledge of international travel, but he is no hardened criminal. To break up a family and ruin three lives seems to me neither humane nor right."

"I need you to know that I'm no angel," said Philip, admitting to short spells in county jail after being found guilty of drug and drink related misdemeanours. "But I'm not a bad guy. All I want is to be back with my family."