Video report by ITV News Security Editor Rohit Kachroo
The detained Isis fighter, who held dual UK-Canadian citizenship, said he was expecting the British government's decision and, after two-and-a-half years in a Kurdish prison, retains only faint hope of Canada taking him in.
Letts, 24, appeared lightly bearded in a white T-shirt and with scratches on his forehead, which the YPG forces holding him said were the result of mosquito bites.
After confirming he was happy to speak on camera, Letts gave his first reaction to losing his citizenship, described Boris Johnson as "ridiculous" and sent a message to his parents.
During the course of the interview Letts also claimed joining Isis as an 18-year-old was "the stupidest thing" he's ever done - though added he "never even hurt anyone".
Once informed of the decision by then home secretary Sajid Javid to strip him of British citizenship, he said: "Obviously it's new to me, I didn't know that until just now.
"(But) I was expecting something like this to be honest.
"I've been here for two-and-a-half-years, they haven't helped me at all.
"It's almost as if I'm not a British citizen anyway."
ITV News Political Correspondent Paul Brand on the Government's stance
Under international law, a person can only be stripped of their citizenship as long as it does not leave the individual stateless.
Letts said he had never expected to be brought back to Britain, adding: "Stripping me of British citizenship and not stripping me is the same thing because they're not going to help me anyway.
"It's just a piece of paper at the end of the day."
Asked if he had a message for new Prime Minister Boris Johnson, Letts said: "What would I say to him directly?
"I don't know, I don't think he'll see this if I say anything anyway.
"I think Boris Johnson is ridiculous, to be honest, I think most of the British population do.
"It's amazing he actually became prime minister."
Though he added: "I know I'm an infamous terrorist and it's not going really going to make a big difference by what I say."
Letts said he "always grew up never being accepted as a British person anyway" and said: "I don't think where you're from is based on a piece of paper.
"I never asked for citizenship ... (it has) very little meaning to me."
However, he appealed for Canada to help him as he said his affections lie with the nation of his father.
"My whole life despite the fact that I lived in Britain, I speak with a British accent and I've never even lived in Canada, I've always felt that I'm Canadian," he said.
"My dad's Canadian. ... I've been to Canada seven times.
"I've no relatives in Britain, everyone's in Canada."
ITV News Security Editor Rohit Kachroo explains Canada's 'furious' response
But he feared his hopes of Canadian officials moving him to North America were an "illusion", despite his willingness to remain locked up.
"I understand I'll be in prison wherever I am," he said.
"(But) Canada has done nothing.
"I had this idea that Canada was a better country (than Britain)."
Asked it he thought Canada could intervene, he said: " If I was optimistic yes, but it doesn't seem very logical at the moment.
"I don't think anyone is going to help me."
They said their son had been left in a “legal black hole” and the government was “shirking responsibility and passing the buck off to the Canadians” - while adding they feared their son had been tortured while being held in prison.
Asked if he had a message for his parents, Letts told ITV News: "Tell them I miss them.
"I know I've said that before.
"It gets more true every day.
"More than two years I haven't spoken to them on the phone, despite repeatedly requesting such a thing."
He said while he had "no capability to get a lawyer" he had been visited by a lawyer who he suspected may have been arranged through his parents.
But he doubted there would be movement in his case, saying: "I have absolutely no rights - I'll probably get in trouble for saying this.
"I can't even speak to my mum so how can I talk to a lawyer."
Letts, who left his Oxfordshire home to join Isis in Syria in 2014, admitted regret while also attempting to justify his actions.
"It was probably the stupidest thing I've ever done," he said.
"I never killed anyone though, I've never taken anyone a slave, I've never even hurt anyone in Isis.
"I only fought the Syrian regime which killed more than a million Syrians.
"I did it with the wrong people, that's true, but... I'm not a murderer and I've never taken anyone as a slave, I've never tortured anyone.
"I'm just a person who made a stupid mistake. And after two and half years of no trial, no nothing, it makes sense that there should be some sort of result."
In response to Letts' case, the Canadian government said it was “disappointed that the United Kingdom has taken this unilateral action to offload their responsibilities”.
The statement from Canada's public safety minister Ralph Goodale said: "The government of Canada is aware that the United Kingdom revoked the citizenship of Jack Letts.
“Terrorism knows no borders, so countries need to work together to keep each other safe.
"Canada is disappointed that the United Kingdom has taken this unilateral action to offload their responsibilities.
“Investigating, arresting, charging and prosecuting any Canadian involved in terrorism or violent extremism is our primary objective.
"They must be held accountable for their actions.”
Prime Minister Justin Trudeau said: "It is a crime to travel internationally with a goal of supporting terrorism or engaging in terrorism and that is a crime we will continue to make all attempts to prosecute to the fullest extent of the law."
Video report by ITV News Political Correspondent Paul Brand
A Home Office source said: “The Home Secretary is not going to be reviewing the decision to deprive a terrorist of his UK citizenship.
"Having British citizenship is a privilege and those who join groups like Isis which take pleasure in crucifying children forfeit that privilege."
While not naming Letts, a spokesperson for the Home Office added: “Decisions on depriving a dual national of citizenship are based on substantial advice from officials, lawyers and the intelligence agencies and all available information.
“This power is one way we can counter the terrorist threat posed by some of the most dangerous individuals and keep our country safe.”
Responding to the revocation of Jack Letts’ citizenship, shadow home secretary Diane Abbott said: “Whenever there are reasonable grounds to suspect that someone who is entitled to return to this country has either committed or facilitated acts of terrorism, they should be fully investigated and where appropriate prosecuted.
"We are not in favour of making people stateless, that’s a punishment without due process.
“Simply removing citizenship may please ministers, but it isn't justice in any sense.
“Government ministers shouldn’t offload Britain’s responsibilities to other countries.
"We have a duty to deal with these cases ourselves, in line with international law.”
They avoided jail after being sentenced to 15 months, suspended for a year.