Well, not really. Yes, it's true that a substantial fraction of current US food production goes to animal feed. Yes, it's true, theoretically, that you could turn all of that into human food production instead. Of course, that would mean we'd all need to become vegetarians, but of course that's better than starving.
But this elides two important points. First, humans can't survive on what is currently being grown. In other words, we can't just stop feeding all of that corn and soybeans to animals and give it to humans instead. We can't live off of a diet that is 75% field corn and industrial soybeans. We would have to change what is being produced, and that would be like turning a battleship. It's doable, but it would take time.
And second, without animals in the loop it's very hard to have a sustainable nutrient cycle. Animals, especially ruminants like cattle, sheep, and goats, can turn otherwise inedible vegetation on unarable land into manure which can be used as fertilizer. So if we do away with the animal agriculture, and turn entirely vegetarian, then we are as a side effect reinforcing our dependence on industrial fertilizers.
Of course, you can argue that that nutrient cycle is already broken in our current system, and you'd be right. But if you want to look at what a truly sustainable, environmental agricultural system would look like, it almost has to have ruminants.
Look, for example, at how Amish farms work. Those guys do it right. Their crop yields are on par with the best yields in big ag. It's a sustainable model.