That would be silly, California is what it is today because it is part of the United States. The ports by themselves bring in a lot of money and being another country introduces two new borders that the United States would want to avoid and go around. It also has a lot of money in the financial sector, which would gain significant extra barriers and costs with the rest of US businesses if it wasn't part of the US. Plus the only places where you get majority support for that sort of thing in more dense urban areas and losing large chunks of the state's landmass would definitely hurt the California economy.