trust me, if there is a world wide crisis that affects agriculture, things will change very quickly. A drought in California is regional, so people wouldn't get to excited about that. Also, food sharing doesn't work all that well right now. there are lots of people starving in different places the world. I tried to look up info on max exporters, US is number 1 and has in the past 60+ years been the only one that really affects international prices. France is listed as 2, but that's because of the high value wine, cheese they sell. Brazil and Argentina are emerging big exporters of basic food crops, and they are increasing fast, the limiting factor seems to be infrastructure to get crops from fields to ships. I grew up on a farm and read quite a bit about world food supply, its not nearly as elastic as you are saying.