There was a time, not so long ago, when you could easily explain U.S. agricultural policy. It was countercyclical and focused on risk management, especially for traditional row crops. There were a few exceptions, like dairy and sugar, which maintained the remnants of supply control. Participation was broadly voluntary and focused on the economic structure of food production and was not deeply politicized. It had a well-developed conservation policy that preserved forests, prairies, and wetlands. Its efforts to protect animal and plant health set global standards. Most unusually for a high-income country, it also aided low-income consumers with food assistance and supported school lunches. Its trade titles did not directly subsidize exports;...