[grandalf]

Perhaps, but don't you think that any war serious enough to warrant a massive shift of global food production would arrive with enough forewarning to allow emergency crops to be planted?

Also, keep in mind that the war would have to involve a hostile Mexico AND Canada and our adversarie(s) would have to block access to the eastern and western seaboards.

Perhaps in a previous era (such as the cold war) where fear overcame rationality on a regular basis, such a scenario sounded plausible. But it is fairly ridiculous today.

It is my guess that whatever third world governments are doing to "subsidize" it is necessitated by other policies that cause harm. Sadly, many third world nations have highly corrupt governments which largely siphon resources away from the average person rather than providing infrastructure, solving coordination problems, etc.