There's never no internet everywhere. Bitcoin is distributed, you just have to transmit it to wherever internet is still running. But if internet is out EVERYWHERE, what the hell happened? Did any humans survive?

Note: I also wanted to recommend as far as resources on this subject NVK (Coldcard, maker of Opendime, Satscard, etc.) with a couple of lectures on how to send Bitcoin transactions over amateur (HAM) radio. https://nvk.org/bitcoin-ham-radio