No, but the taxation often provides the tipping point.
A national currency is marked by 2 things: that you can (or must) pay your taxes with it, and that the employees of that government (most especially the military) accept it in payment. As long as both of those are true, even with serious inflation, the national currency has value.
That is only pertinent to the internal market value of the currency and only to a limited degree. The North Korean won and Libyan dinar are pretty worthless outside of their native nation states. However a national currency can even internally spiral out of control even where there is still the requirement to pay ones taxes from it and have it accepted as payment (think Zimbabwean dollar).
Any currency can be massively devalued by the creation of more of itself in excess of the perceived value of the currency. The more notes that are printed, the less the value of those in circulation becomes. This is why quantitative easing and similar solutions will not work. Come back in 5 years if you do not recognise this fact today and we'll talk then.
The strength in Bitcoin in this matter is that one cannot just run a shell script to create a few million more Bitcoins. Because the release of the unit of exchange is fixed there is a certain degree of security to it. Okay, so there is no major tax-raising government entity behind the currency. Does that mean it is worthless as a medium of exchange? Of course not. A medium of exchange is just that and no more. The value of a one hundred dollar bill is only what you are able to exchange it for, which is entirely dependent upon the environment you find yourself in.
Personally I would even argue that the claimed weaknesses of Bitcoin (decentralised, no government backing) could be a foundational key strength of the currency.