A better example would be specifically corn used for ethanol because driving a car is not essential for survival.
The other two examples seem valid. Replacing part of your meat consumption with corn would reduce the required agricultural land.
An interesting quote which echos what you're saying here:
> That means that table corn, carrots, cabbage, apples and broccoli are all examples of what is called, paradoxically, “specialty crops” — and they largely don’t get the same support as the heavily subsidized industrial crops.
The absurdity here is that "specialty" crops are what you might call "food". Most corn is "what my food eats".
If survival was important, people could switch trivially. I would take a 99% vegetarian diet in exchange for not dying. Problem is that the costs may be collectivized, and weighted towards future generations.
"The present area of sugarcane (Saccarum officinarum) is about 13 million ha with a total commercial world production of about 1254.8 million ton/year cane or 55 million ton/year sucrose. (FAOSTAT, 2001)." [https://www.fao.org/land-water/databases-and-software/crop-i...]
That climbed to 1.9B tons by 2020. [WP ... 40% in Brazil] And 13Mha = 130,000 km^2 > 50,000 sq.mi. About the size of Iowa. And then, there's almonds.
https://www.usda.gov/sites/default/files/documents/coexisten...
The error being made is assuming that corn cultivation being significant to global food supply means that corn is being cultivated primarily for food.
Production of both is currently rising rapidly.