Okay, I always said this is a stupid question because such a day won't come anytime soon. But a similar incident happened to me and my country mates. I have never spent a day without an internet connection since I first started using the internet. But this time, I and my country mates had to live without internet for the last six days.
I and my country mates just came out from six long days of internet blackouts and are feeling fresh for now. But, I cannot tell you how it was without the internet. Unable to connect with friends, unable to pay bills, unable to works and countless things which I cannot even remember now. But, since Bitcoin does not depend on a single country, I still believe that day won't come.