The point to any preparation for any adverse event is to prepare more than one solution to a problem, and to have a solid understanding of your actual adversary. By asking that question, you have already defeated yourself on the sake of whomever you have decided is the dominant force. This is the sort of nihilism that stops us from meaningful change, because we destroy ourselves in either sloth or despair.

Won't they get jammed? Yes, absolutely, on local levels. This is electronic warfare and happens in any actual battlespace.

Does that mean it is completely useless in emergency situations (of which civil war is one)? No.