If there was free trade and corn wasn't fed to animals there would be enough meat and health and wealth for everyone.
Humans need 250grams of protein a day, some can come from plants, some from eggs, some from animals.
Currently what happens is that corporations lobby governments to protect local food markets under the guise of food security so that grass fed meat cannot be imported from sparse populations with lots of pasture into dense populations short of pasture.
The dense population then gets obese and mentally ill on corn-fed local beef while the corporations profit from the margin between feeding an animal corn or feeding it grass while sidestepping the cost of negative externalities. A hectare (10,000 sq m) of corn will grow 30 tonne of corn in a year, a hectare of pasture will grow 16 tonne of grass in year on the same land. The corn progressively wrecks the land and needs to be replanted every year. The pasture is perrennial and preserves the carbon content of the soil which is a massive and under reported component of the carbon cycle. 10kgs of grass or corn make 1KG of meat. Humans already have a surplus of corn, they are currently turning it into biofuel.
If you factor in the soil preservation then pasture plus grazing animal is the most economically viable sustainable option because double yield of corn comes at the price of the health of the soil and the humans and the animals that it's fed to. Look at the skeletal record around the time of it's invention for the associated decline in health despite the calorific surplus. Look at why corn fattens cattle.
If land is put to it's best economic use the problem slowly corrects itself as the human population naturally declines with improved standards of living.
If you were able to buy grass-fed hormone free argentinian or south african or russian mince in Walmart at true cost the world and the US would be healthier and wealthier. The invisible hand works as long as negative externalities are acknowledged truthfully but there is a lot of profit in obscuring them.
There is also lot of room for trees around pastured land to offset the methane and sheep produce less methane than beef plus non inflammatory milk plus wool.
Not to mention the greenhouse gas effect of that many cows, which is much higher for grazing cattle.