Bitcoin, for now, is not suitable to become a national currency of any country. Bitcoin's value is too volatile so a product or service will always change in price with respect to the price of Bitcoin. Also, a transaction fee is there with every transaction, this is not practical in using in a daily basis. It will be hard for the government to control the scenario. So if a country will make Bitcoin as its national currency then they have to regulate it first.
Bitcoin is more than a national currency because in all form of currency in every country we could actually used bitcoin on transaction just consider on the acceptance of bitcoin to a specific country. But if you are going to look at bitcoin as a form of universal currency that can be used in all country with all types of transactions.
Bitcoin can be more, but I agree with first comment, bitcoin is still not suitable to become national currency in one big and developed country, maybe in some little island state yes. Until bitcoin become suitable To fulfil all parameters that one serious currency should have we will see the same as what is happening in Japan currently, bitcoin will be legalized currency, available for using, trading, investing, aside from their own national currency.
I said Japan, but there are other countries that did the same, this will be sort of test, we need to wait a year or more to see results of that.