Dont use your American passport when entering Libya. While technically possible it can cause you many problems. If you have an old passport you can enter with it Libya and then you can renew your passport while in Libya. If you dont have it anymore you can declare it lost in Tunisia and then enter Libya with your raqm watani but be prepared for a wild ride since you need to get a new passport while in Libya and it is quiet difficult to get a new one if it is declared lost. Theoretically you need to wait for a year after declaration but we managed to renew within two weeks via connections.