To put it in very simple terms, yes. But often, a nation acting in it's own interest causes some degree of harm somewhere else. And therefore, a collection of diverse nations will not agree on what's 'best' for the world, for regions, or for blocs.

If sovereignty were abolished, with the (magically induced) approval of nations, it would be a different story. Without borders, "good" and "harm" would have two ends - municipal and global. And then there would be conflict between those interests.

Now, if one were to introduce a new idea, an idea of humanity existing as a body above nations, above blocs, above regions and municipalities, perhaps there could be some agreement as to what's good for the world - especially speaking in terms of the mutually assured survival of humanity, and not the constantly threatened survival of nations. It would not require imposing a universal government, or abolishing sovereignty. Already there is an element of this new idea, and its motions are carried out by some of the more noble acts of the UN, certain multi-national charities, et cetera. But still, independently acting groups like nations, banks and corporations threaten this concept by acting against the interests of vast groups of people (even entire continents) in the spirit of personal gain.