The software engineer is still barred from entering the US despite being cleared by the Canadian government last year of any links with terror groups following an official inquiry.
Ottawa apologised and paid him compensation of $10.8m in January.
On Thursday Democratic and Republican legislators apologised to Arar and said George Bush, the US president, should follow Canada's lead, admit the mistake and say sorry to the Canadian.
Bill Delahunt, a Democrat, said: "The Canadians have acknowledged their mistake. It's this nation, this government, this administration, that has failed."
"It reflects an arrogance I don't like to see in our government"
Dana Rohrabacher, US legislator
Dana Rohrabacher, a Republican, said the US made a mistake but "has been unwilling to own up to it".
"It reflects an arrogance I don't like to see in our government," she added.
A White House official said she was not aware of any plans to issue an apology to Arar.
Arar's deportation was based on information from the Royal Canadian Mounted Police who suspected him of being an Islamist extremist.
Describing his ordeal to the House of Representatives Judiciary and Foreign Affairs committees via video link, Arar said he still suffers from nightmares, feels emotionally distant from his wife and children and has had trouble working.
"I am not the same person I was. I have come to accept this as part of my new life, but I want to make sure no one else goes through what I went through," he said.
Arar told the committees he was beaten with electric cables, kept in a cell measuring 1.8m by 0.9m and did not see sunlight for six months.
"I am not the same person I was ... I want to make sure no one else goes through what I went through"
Maher Arar, Canadian "rendition" victim
He said Syria refused to let him renounce his citizenship when he emigrated to Canada as a teenager.
"The most fundamental question that has not been answered yet is: why did the US government decide to send me to Syria and not to Canada?" he said.
The US government has sought to dismiss Arar's case on the grounds that it would violate state secrets.
It acknowledges conducting "renditions" or secret international transfers of terrorist suspects, often to countries with dubious human-rights records, saying the programme has prevented further attacks.
Dean Boyd, a US justice department spokesman, said Arar was deported to Syria because he maintained dual citizenship there, and that Syria had assured the US that Arar would not be tortured.