I saw Joe Biden released a plan to buy American products in order to maintain domestic supply lines and stockpiles of essential commodities. Surely considering the amount of funding the government supplies in farm subsidies indicates an unwillingness to allow agriculture to lose in the marketplace, and would consider agricultural commodities as strategic resources. Hypothetically, if there were a way to nationalize the agriculture sector, would there be benefits to American farmers? The economy? Our ability to adapt rapidly to climate change?
I think you are using the term "nationalize" to mean the US government buying US farm products. The US is a major exporter of meat and grains and these products are typically more expensive in other countries than they are in the US. So the US consumer has every incentive to buy US farm products.
The USDA does already purchase enormous quantities of US food for school lunch programs and for food pantries. If it purchased any more, it would either have to store the food at some expense or give it to US consumers at a discount. These US consumers would then purchases less food from US farmers.