Bitcoin and Federal Reserve Notes (USD) are two very different currencies, though they can both be used to make purchases from a range of vendors throughout the world. Bitcoin is a decentralized network as well as a currency that is used on the network. Federal Reserve Notes are colored pieces of paper that represent a centralized fiat currency.
I believe the decentralization of a currency is vital to it's long-term success. Without a central entity in complete control of the currencies supply, the 'store of value' characteristic will be proportionate to the currencies use. For example, the value of bitcoin over-time is dependent on it's innovative features such as its ability to send wealth to the other side of the world without borders or an intermediary financial institution taking a cut.
Federal Reserve Notes, on the other hand, are pieces of paper used to signify a receipt of debt. They are printed out at will and because of this, the issuer has complete control over the currencies value. If the Federal Reserve decides to print more notes, the value of each note decreases. This is a way for governments to control a monetary system and enslave the people that use it.