Why think about it now? I hope that the world war will never happen again.
It is okay to think about something that hasn't happened and this can be considered as the anticipation if bad thing happen to the world and it doesn't have to be world war. I also hope that no more world war will occur in the future, we want to live in peace and remain safe in carrying out our activities.
Gold has a physical reference in the world, bitcoin does not. If the entire Internet is turned off, then Bitcoin will quickly begin to lose value, because those segments of the world where the Internet will still exist will sell it fearing that its price will fall due to the Internet disconnection. In order for bitcoin to develop, a certain level of stability in the world is necessary. World wars will interfere with this.
I agree with you, the internet is an intermediary that will connect the entire bitcoin network to all user. Without the internet, bitcoin is just a name and has no value. Meanwhile, world wars can affect the global economy and crises will occur. The stock market collapses and the crypto market will also be affected. I don't think that bitcoin can survive if the world is destroyed by war, and at least it will reduce its value.