Due to the Department of Homeland Security, your car may very well be stuck behind a log jam of crap awaiting inspection at some port. I doubt it -- but there is a chance. The ports are totally overloaded with stuff coming into the US right now -- and none of them have the manpower to keep up with the burden. Who knows? Maybe some dork with a badge is gumming things up.
Regarding shipment of your car, there are a number of logistics that need to be coordinated -- not all of them in GM's control. The Union Pacific railroad bought the Southern Pacific railroad a few years ago -- and the integration has been a complete nightmare ever since -- complete with train cars of grain going bad, etc. because they can't get through some of UP's system bottlenecks. And all the cars that arrive in Northern California by boat are loaded at a former Southern Pacific terminal now owned by UP.
My guess is that the cars are in -- and are simply waiting for UP to get their act together. Trashing someone in Pontiac customer service and demanding a car "right now" just isn't going to work. Really, what do you expect them to do? Put you on hold, fly over to the port of entry in Benecia, find your car, put it on a flatbed, send the flatbed over to Oakland International Airport, then load it onto a FedEx MD-11? Granted, the person you're working with should be empowered to make something happen for you -- but, unfortunately, they have no authority to go to a dealer and make them release inventory to another customer.
At this point, as another post indicated, your best bet -- iif you have to have the car right now -- is to search existing dealer inventory and try to work out a competent deal. Otherwise, be patient.
By the way -- whenever you order a car, always have an escape clause written into the contract allowing you to exit without penalty if a predetermined commitment date is not met.