Corn was until recently a very area specific crop. The 'corn belt' is well named.
Greenland is a massive island and under Danish 'rule'. I don't think they'd appreciate being called North American.
The Western Hemisphere isn't just America, iimmc....it includes most of the UK, Ireland, Portugal, big chunk of France and Spain, enormous part of Africa, etc., too.
On the whole we're lucky here because it's fairly easy to find gluten free oat products and the prices are dropping as the volume increases with more purchasers.