"If the UK accepted me, then I'd go back to the UK It's my home. But I don't think that's going to happen," he said in an interview with ITV's Rohit Kachroo.
Letts, who was born to a British mother and Canadian father, says he is unsure if his Canadian passport is still valid and doubts officials on either side will come to his rescue. When asked whether he felt British or Canadian, Letts said he "felt British."
"I don't think I'm going to be given back to Britain, for example, or some Canadian official is going to come and help me because like I said, no one really cares," he said.
When asked what he thought of terrorist attacks in Paris, Brussels and Manchester in recent years, Letts said: "To be honest, at the time I thought it was a good thing." The Islamic State claimed responsibility for the attacks, which killed 185 people and wounded hundreds of others.
"This is what war does to you," Letts said. "You have this idea of 'why shouldn't it happen to them?'"
While Letts is accused of journeying to Syria to fight alongside Isis, his parents, John Letts and Sally Lane, have always maintained their son's innocence, saying he left his hometown of Oxford to help refugees in Syria. Letts' parents are charged with sending him money from the United Kingdom but have denied the charges of funding terrorism. In an interview with the BBC in 2017, Letts' parents said they had tried on numerous occasions to get Britain and Canada to help bring their son home.
According to ITV, Letts has not been stripped off his British citizenship - unlike British teen Shamima Begum, whose citizenship was recently revoked by the British government after she left her home in London to join Isis in Syria.
Begum, who was also interviewed by ITV, recently gave birth in a refugee camp and had hoped to return to Britain for a better life with her child. Begum's case ignited debate in Britain, with many protesting the idea of her return, while others declared that she needs support.
Both Begum and Letts appear likely to be put on trial for their involvement with Isis if they ever return to Britain.
The desire of foreign Isis fighters in the Middle East to return to their home countries has become a divisive and delicate issue. While President Donald Trump has urged European countries to take back their fighters captured in Syria, he announced last week on Twitter than he would not allow Hoda Muthana back into the United States.
Muthana, a 24-year-old from Alabama, married an ISIS fighter and currently resides in a refugee camp in Syria. She says she was "brainwashed."