I think this year's drought that has hit American Agriculture so hard, with "half of the US counties deemed natural disaster areas", only strengthens the argument that factory farming cannot efficiently feed a nation.
When nearly all of the meat (beef, chicken, turkey, pork, and farm raised fish) produced and sold in the US depends on annual monocrops (GM corn and soy) as the primary feed source, saying we have all our 'non-cage-free' eggs in one basket would be a profound understatement. With the majority of the hundreds of millions of acres of farm land stretching across our nation unnaturally occupied by one of two crops, our nation's food system is greatly dependent upon four things; good rainfall, chemicals, chemicals, chemicals...
Nature dictates the rules; diversity (polyculture over monoculture), fertile soil, and rain. A successful organic sustainable farm helps guarantee the first two requirements are met, while factory farming on the other hand requires chemicals and GM seed to accomplish the same feat. With the soil continuously depleted of all its nutrients due to harmful deep tilling in order to make way for overly dense populations of single crops, any favorable yield requires unnatural help. Collectively these infertile farm lands require billions of tons of chemicals in the form of fertilizer to add much needed nitrogen, herbicides to prevent the only thing that effortlessly chooses to populate these otherwise barren deserts (weeds), pesticides to kill all of nature's opportunistic insects that effortlessly feed on these helpless nutrient lacking crops, and of course the round-up ready GM seeds.
And even with all this chemical warfare on the side of factory farming, all can easily be lost if the winds of change choose to blow the rain clouds away. Sure, sustainable farming requires water just as factory farming does, but in a sustainable farming model you have smaller, local organic farms with more pasture than monocrop. You creatively use the landscape given to you and gently mold it into something that favors your sustainable farming needs. Instead of knocking down and plowing over all standing trees to make room for fields of corn or soy, you leave a nice thick perimeter encircling your pastures (sustainable = pastured), promoting refuge for smaller animals that can feed the predators that would otherwise prey on your livestock. The trees and brush also do a good job of feeding the soil as well as soaking up any pollutants that may be in the ground. Utilize low lying areas to create ponds instead of tilling and seeding. Use livestock (pigs and chickens) to till for gardens instead of heavy equipment. Plant only enough grains to feed those omnivorous animals that can consume them as part of the diet, like chickens and pigs. Let Pasture dependent animals (cattle) graze, feeding them hey in the winter months not grain. Use proper pasture rotation methods as practiced by successful organic sustainable farmers such as Joel Salatin, and make it your goal to build topsoil not deplete it.