There are places where even posing this question - at least if it clearly applies to the corresponding nation - is extremist speech. Nations, like all other corporations, are like organisms themselves. They might still act beneficial to their population, but never at the cost of their own survival.

Nations were useful, particularly when almost all problems were local problems. Doesn't mean it's an ideal top-level organization for XXI century.

You have bodies like Germany or the US, which function as a federation of states. Looking at Germany and EU, you essentially have states within a state within a sort-of state. You can stack governments recursively, so it's possible and in some ways desirable to have a single one at the top level.