Actually, it is a literal monopoly on many things. For example:
> California produces a sizable majority of many American fruits, vegetables, and nuts: 99 percent of artichokes, 99 percent of walnuts, 97 percent of kiwis, 97 percent of plums, 95 percent of celery, 95 percent of garlic, 89 percent of cauliflower, 71 percent of spinach, and 69 percent of carrots (and the list goes on and on).
Those other states are monocultures of federal subsidies like wheat, cotton or corn.
The monopoly exists because they pay artificially low prices for water. Those crops grow just fine in many locations and even controlled environments. If ag left the Central Valley, we would find a way. Likely not even a difficult problem and certainly not a problem if the money was used to decentralize Central Valley production.
I’m fine not eating salad in December if you give all the water back from the Colorado river.