I'm assuming NZ didn't sign a free trade agreement with the US like Australia (the US-Australia free trade agreement ensures US copyright law applies to and overrides Australian copyright law).
Where on earth did you get that? Yes, the free trade agreement has affected Australian copyright in some limited cases, but it nothing like as clear cut as you make out there.
As a random example, the book 1984 is out of copyright in Australia, but will remain in copyright in the US until 2044: http://en.wikipedia.org/wiki/Nineteen_Eighty-Four#cite_ref-1...
There's been lots of rumbling about it when one of our honchos visits USA's honchos, but the application of the US Intellectual Property laws is one of the big problems I have with it.
I think it's unlikely to happen any time soon. Barack Obama needs to get re-elected. To do that he needs the Iowa caucuses. He's not going to help out New Zealand farmers at the cost of the support of American farmers.
Can you elaborate on this? I understood treaties to have no legal force in Australia until domestic laws were passed to give them force. I know there are exceptions to this rule (like Teoh) but AFAIK they don't involve overriding domestic law