Assuming something resembling the OTL Confederacy, nothing closer to the Pacific than El Paso? Russia might offer, CS would refuse, it's too far away and utterly useless for plantation farming. On the other hand, if something like the Pico Act goes through earlier and the resulting slave state in SoCal joins the Confederacy so that they actually have access to the Pacific... Still probably no, for the same reasons. It's not impossible but there's just not really a good case for it.