Not exactly true. California is the top agricultural producer and produces almost twice as much as number 2. Minnesota and Illinois are also very high on the list.
Seem my comment about where most if the water comes from to water those crops. We could sell them water by the spoonful after we build the Trump Dam and Water Reclamation Project on the Colorado River.
And the agricultural areas of CA, MN, and IL are red as well.
You are thinking at the state level. You need to adjust your perspective and think at the county level. If the country breaks apart, states will dissolve as well.