We don't have the equipment to do this at the necessary scale. Corn just isn't used as a survival crop this way, so there's never been an economic need to invest in the machinery to do it.
We probably do have the infrastructure to keep producing wheat bread in mass quantities. Do we have the peanut production and processing infrastructure to handle peanut butter becoming our primary protein source? I doubt it.
And of course with soybeans... they would need to be dried or canned, packaged, stored, and shipped. Doable but different from what we are currently set up to do.
And of course there's the psychological impacts of all of that, which again are probably oreferable to starving but wouldn't be good. People fight wars (or gang wars)over this kind of thing.
As a soybean farmer, and one who has focused on IP soybeans for the human market for most of my career at that, unless I am misunderstanding you, that is exactly how we do it. The beans are harvested dry, packaged, stored, and then shipped (primarily) to the Asian markets who are interested in such product.
The trouble in North America is that few know what to do with them. To be honest, I have never even tried my own product. I also grow navy beans and have cooked with them. They are more of a common staple in these parts. But they are also a much more fickle crop. You're not going to easily replace soys with other edible beans.
Why not? Beans and rice, potatoes and milk, bread and peanut butter. Those are all nutritionally complete diets, as in you won’t get any deficiency diseases eating nothing else for a year. Feed corn and soybeans has carbs and protein. It might be nutritionally complete by itself. Add cabbage or some other leafy green vegetable and 100g of meat a week and you’ve got a monotonous, bland, healthy diet.
I’m not saying this is pleasant, feed corn tastes pretty awful but you absolutely could live off a diet that was mostly beans and corn.