Well, no electricity, and no internet connection would kill BTC for sure! You wouldn't be able to make any transactions without these.
Other issue can be all the countries in the world ban BTC, but this will not restrict it's circulation, as no internet connection do!
I don't think that's the main reason because we can substitute solar energy to run our desktop and internet. I think if all country would agree to ban bitcoin or no one would like to buy bitcoin.