Over reliance on California is foolish in the best of times. Its an arid state with a potential for serious drought always looming.
Crops should be regionally diversified. 2012 is a perfect example. The midwest apple crop was virtually non existent but the northwest apple crop boomed. Root crops and leafy green vegetables also do very well in those regions.
That said, abundance is a good thing. If we grow more than we need we will never have a shortage.
That is true, but the unintended consequences should be factored in. Abundance tends to lower prices, but production costs don't tend to follow. Less incentive to produce, or subsidies required. A balance has to be reached.