The US corn crop has been averaging around 13 billion bushels/year. Fifty-six pounds per bushel, 2.15 gallons of ethanol per bushel. Works out to just under 28 billion gallons of ethanol if the entire corn crop was converted. To produce enough ethanol to replace all the gasoline used in this country would require planting over 400 million acres, compared to the current 91 million. In reality, it would take around 500 million acres, or so, because ethanol contains a lot fewer BTUs than gasoline. There aren’t that many acres of arable land in North America, and most of the land suitable for corn production is already planted to corn. So, no, it wouldn’t be easy to grow 10 times as much corn. In fact, it wold be impossible.