California would lose it's military personnel, as it is the military of the USA.
Lose how? Like, a Californian wouldn't be given the chance to stay with his or her state as it exits the Union?
That seems...unlikely.
And the equipment leaves too.
Our tax dollars paid for the equipment. Some of it is rightfully ours. And it's not like the US is terribly discerning who they sell stuff to.
Plus, a lot of it was developed here.
Including all the shipping vessels and equipment.
Can California afford to establish its own military?
Can it buy or build enough equipment and man-power to establish it's own military defense?
California is a rich state. It represents about 12% of the US population, but about 14% of the country's GDP. Economically, it could save money not subsidizing the rest of the country.
Of course, I have to hope we wouldn't get into a situation where we have to spend so much on military. But, it absolutely could, if it came down to it.
Can California build or buy enough ships for import/export trade?
Actually, in California, we practice an economic system called "capitalism", where the government doesn't own the things. You should really give it a look.
Would the USA stand for California having nukes?
What would we need them for?
Would the USA allow California to use it's air space?
That question can be asked in both directions. And it's not like California is land-locked. You know what would be annoying for the US? Having to fly around California to get out over the ocean.
It's not going to happen. It's fun to run scenarios, but it's not going to happen. We haven't given up on this backwards union yet.