No Us dollar is national currency of USA,any country need to have his own currency,look euro currency ad look what is happening with Greece and Portugal
Yeah your right bitcoin is just a digital currency that you can use only in online transaction you can not use it in offline if internet is gone you cannot use it unlike usd or fiat you can still use it anytime anywhere offline or online.. its still a money..
very precise, and also the use of bitcoin is still limited, usually only for a certain person, and everyone is not likely to use bitcoin, but the dollar can be used by everyone, without restrictions