We would advise you to check with local law enforcement officers or the South Carolina Department of Motor Vehicles (DMV) to find out for certain if you can legally drive with a broken out back window however we believe that you could be cited for a mechanical or equipment violation with your motor vehicle if you drive you car in that condition.
According to Section 56-5-5010 of the South Carolina Code of Laws, titled Safety glass in motor vehicles, no person shall sell any new motor vehicle nor shall any new motor vehicle be registered unless such vehicle is equipped with safety glass wherever glass is used in doors, windows, and windshields.
The law continues on to say that the foregoing provisions shall apply to all passenger-type motor vehicles, including passenger buses and school buses. But in respect to trucks, including truck tractors, the requirements as to safety glass shall apply to all glass used in doors, windows, and windshields in the drivers' compartments of such vehicles.
The Department of Motor Vehicles shall not register any motor vehicle which is subject to the provisions of this section unless it is equipped with an approved type of safety glass, and the department may thereafter suspend the registration of any motor vehicle so subject to this section which it finds is not so equipped until it is made to conform to the requirements of this section.
Thus it would appear that you could be cited for breaking a SC law and have your car's registration suspended if your car is found to not be equipped with the proper safety glass in the rear window.
If you have comprehensive coverage on your vehicle you should be able to make a claim for the broken back windshield and according to the SC DOI the deductible is waived for private passenger vehicles who make a glass claim such as this.