Most would agree that the wellbeing of people living in other countries matters. Since people in poorer countries are more likely than people in richer countries to face severe problems that could be solved at little cost, it is often a good general heuristic to focus one’s attention on impoverished parts of the world, rather than looking for giving opportunities in one’s local area (assuming one is from a richer country).
Brown, Eric & Pauline Kleingeld. 2013. Cosmopolitanism. In Edward Zalta (ed.), Stanford encyclopedia of philosophy.
A discussion of its philosophy, including a variety of different ways in which the term has been used historically.
Hallquist, Topher. 2014. Cosmopolitanism.
A discussion of its importance to effective altruism.