Exactly, can't be done. And ISPs all lease from someone else to get on the nationwide and int'l backbone. If they take down ISPs, maybe you can find something.  If they take down the ACTUAL internet, only a strictly p2p homegrown mesh network would work, like bridging router-to-router across town. Even then you're limited to what individual share on your own network. And they have teo have tools to do it.