Little New Zealand flags on boxes won't solve this. KiwiSaver might.
Environmentalism can serve a similar purpose to nationalist campaigns. One of the current fads in Europe is the idea of "food miles", that consumers should attempt to eat produce produced locally because transporting it has less of an impact on the environment - most importantly CO2 and other greenhouse gas emissions. It's big in the UK (although Walmart in the US is making noises about it) and, as you might imagine, is enthusiastically supported by British farmers.
It also has obvious implications for NZ exporters - and if your image of NZ mostly involves 40 million sheep, consider that New Zealand is expected to earn more this year by exporting wine than by exporting wool.
Problem is, it doesn't work.
Check it out - research from Lincoln University (pdf) and a report on UK research - when you take into account efficiency of production, greenhouses vs fields, transport on trucks vs shipping, integrated production chains - food produced in NZ, in Southern Europe, in Africa still has less of a carbon footprint than food produced in the UK. The same probably applies to the US, which I would imagine has even more carbon intensive farming techniques than the UK, given the size of the country and the reliance on mechanical inputs.
How the CO2 emissions compare:
UK New Zealand
2,849kg CO2 per tonne of carcass 688kg CO2 per tonne of carcass
3,720kg CO2 per tonne of lettuce (indoor production) 3,560kg CO2 per tonne of lettuce
Apples (in May when off season in UK)
UK New Zealand
271kg CO2 per tonne of apples 185kg CO2 per tonne of apples
35,000kg CO2 per 12,000 stems 6,000kg CO2 per 12,000 stems
More resources here.
Assessing carbon emissions is a useful exercise, and one which puts environmental decisions in the hands of buyers. Various exercises are being taken to standardise these sorts of calculations - I know that MAF is working on it. But "food miles" is a misleading simplification that seems to be a greener looking equivalent to waving the flag or slapping packages with pictures of kiwis, or bald eagles, or Lizzie Windsor. If someone tries pushing the idea on you, ask who is sponsoring it and whether the science adds up.
On the other hand, it's Saturday morning, and I'm off to the Waitangi market to see if I can pick up some cheap veges directly from the farmers at the stalls...