I had thought that in European usage, ‘corn’ was a generic term for cereal grains, such as oats, wheat and rye. What we call ‘corn’, they call, ‘maize’, with all due respect to the Native American lady on those old Mazola commercials.
I can see your point that this may all be about semantics/language. Perhaps that old saw about Britain and the US being separated by a common language is to blame. During my 3 years in Europe, corn/maize was not presented to me as food. My understanding was Europeans saw corn/maize only as an animal feed. I wonder if an encounter with a properly roasted ear of corn at an American picnic would offend them or change their mind about corn/maize.