The *only* reason I could see this statement being true is deep water ports.

As much as "the other 49" disregard how much California contributes in agriculture...I think Californians disregard how much "the other 49" contribute water, electricity and refined petroleum.

Frankly, I think California would ultimately be just fine long-term but would be in for a massive near-term shock should they successfully secede from the USA...which they won't.