No, it wouldn't.
You are confusing high-valued luxury foods (e.g., artichokes, almonds, and arugula) with basic calorie sources (e.g., corn and wheat). The latter category is the one that makes the difference when it comes to starvation.
California produces only a very small percentage of our calories. No one is going to starve to death if they can't get fresh arugula in January.
See? That's why Calexit will never happen.
A military occupation shuts down all sectors immediately and they absolutely will not come back up for years. Look at what the Taiwan quake did in semiconductors. Now scale that up.
An orderly exit allows the rest of the country to continue buying California products.
Those in power will do whatever to prevent Calexit from happening in the first place.
And so if Calexit happens, will we have San Diego exit from the Republic of California too?
If California gets crushed, the rest of the country will starve.
And you really think that a military that couldn't pacify a city with a bunch of camel jockeys carrying AK-47's could pacify Compton let alone something the size of Los Angeles or San Francisco? Good luck with that.
Calexit won't happen because Californians really don't want it. We're a pretty level-headed bunch even when Cousin Cletus Red State shoots himself in the foot with his loaded gun--again.
The problem is that Trump and the Republicans are incompetent enough to actually do something stupid enough to galvanize Californians the wrong direction. THAT'S the real danger that could cause Calexit.