IF the whole world ban BTC at first BTC will Crash very hard but only for a few month, Demand will be increased while there will be no Legal Seller, All trade will go to undergrand and  Black market and illegal traffic, sellers will start to selling BTC 50 X more than current price. BTC will be more expensive, As simple as that,
That was an answer for these who said BTC will die if whole world Ban it, So no BTC never Die.