NZ is food independent, though. Sure without international trade they’d be limited in their pallete but they could lose near 50% of their farming efficiency before falling below the independence threshold. Speaking from experience it is actually a remarkably idyllic place for humans to live.
That might not work because, well, we have been told by those who went into the Kremlin when a select few were allowed in that the Soviet's response to nuclear war is 'fuck everyone and everyone gets fucked'. It is likely that
everywhere got nuked with a dose of anthrax designed to render breadbaskets
absolutely unusable without concentrated efforts on cleanup with sophisticated equipment.
The US would likely be safe given that it was all but directly stated that the US had an SDI grid setup (given that
House got his hands on
three SDI grade laser cannons (with all the equipment
that entails) before the war, installed them on the Lucky 38, and despite not being fully operational took out some 70 nukes headed towards the Mojave alone), the rest of the world, however?
Fucked. Morrocco might have an SDI system given the
holy shit levels of trust and friendship between the two, but that's probably the only place on Earth other than the units in China (which would likely have some truck-mounted SDIs to ensure that Chinese ballistic missiles don't screw with the US forces there) that would have them.
Remember, the SDI network node in
Boston managed to get all but one nuke that was headed to the metropolitan area, and the one that did
was off target. This is on top of being caught completely flat-footed by China's super-stealth subs that would make the
Red October green with envy, getting degraded by said subs launching at angles so flat that they might just be firing in a straight line, and the fact that everyone and their brother firing the nukes at everyone. If anything, the situation that the US SDI network faced was probably the equiv of having every incoming missile in missile command being MIRVs with surprise-buttsex missiles at a flat angle...