We are already using 56% of the water in the country to feed cattle in one form or another.

I'm just saying is that using meat to feed people is inefficient compared to using the same resources to grow vegetables, grains and fruits.

Whether or not it is possible to convert over all cattle ranching activities into ordinary farms is another question.

It depends on the climate.  Inuit lived on a diet composed almost entirely of meat for thousands of years.  It was a more sustainable choice than farming.  (Though if the climate keeps warming, that may change.)  
What do a small number of people (40,000) living close to the Arctic circle have to do with sustainability of the methods used to feed 300 million Americans?
The question is "Can sustainable agriculture feed the world," is it not?