Answer:
It tells us that agriculture is a politically-sensitive sector, and agricultural protectionism is very common not only in the US, but also in the rest of the developed world.
In most trade agreements, countries add protections for specific primary sectors. The rationale is protect farmer's incomes and modes of living, but the economic reality is that these subsidies tend to produce either higher prices for consumers, or overproduction. In the US, for example, many analysts argue that corn subsidies are directly related with the high obesity levels in the country, because so much corn is produced that corn syrup is added to a wide variety of foods.
