if you are considering it as a national treasure, no it can't be. In order to be a national treasure it has to belong to a nation or a if i'm not mistaken a group of nations it can also be. Bitcoin does not belong to anywhere but instead to everywhere and everyone who has any portion of it.
As for a national asset, well, that can be done yes. Actually there is a small principality that has BTC as his current coin https://en.wikipedia.org/wiki/Principality_of_Pontinha