The strike was temporarily resolved last Tuesday-- the offer still has to be ratified by the workers, but they were supposed to be back at work last week. By around Monday, Canadian National expected normal operations. That doesn't mean that backlogs of shipments would be resolved, but that rail operations should be back to normal.
At least GM didn't close the Lansing plant, Ford (temporarily) shuttered a Canadian plant since they could not get anything to build cars.
As far as why a car would go to South Carolina on the way to North Carolina, transportation companies (air, ground, and rail) cannot ship the main longhauls point to point, the cost is too high. The hub and spoke system is the most efficient and fastest way to transport goods.