Affleck directs and stars in Argo, which tells the story of six US diplomats who escaped the takeover of their embassy in Tehran in 1979.
The film suggests the diplomats were turned away by the British and New Zealand embassies before being taken in by Canada.
They were eventually whisked out of Iran in early 1980 in an elaborate ruse by the CIA which disguised them as a film crew.
During a backstage press conference following Argo's Academy Award win for Best Picture, Affleck said: "Let me just start by saying I love New Zealand, and I love New Zealanders."
Affleck went on to say that despite it being a historical movie, making a three-hour film involved making "creative choices".
"It's tricky; you walk a fine line. It's not an easy thing to do. You try to honour the truth, the essence, the basic truth of the story that you're telling.
"The story that we're telling is true ... it's constructed as well as it could possibly be."
It's not the first time Affleck has defended his decision.
He told the New Zealand Herald's TimeOut magazine last year that he struggled with the portrayal because it cast Britain and New Zealand in a way that wasn't "totally fair".
He later told the Telegraph: "I was setting up a situation where you needed to get a sense that these six people had nowhere else to go."
"But I believe it was New Zealand who turned them on to the Canadians, so it wasn't merely, 'Oh, we're going to turn you away'. It was more about where was the best place for them to go.
"And the truth is that above all, the Canadians were the most heroic in that sense and in the movie. It does not mean to diminish anyone else," he said.
Argo won Oscar trophies this week for Best Picture, Best Adapted Screenplay and Best Film Editing.
