'World Literature' is a marketing term used to denote foreign writers. These are rigid categories and foreign writers are mutually exclusive from local ones. It is largely a promotional term for writers overseas. Coined by Goethe in the 18th century, it is pretty much an out-dated term used at a time when countries were beginning to unify and when nationalism was rife. The term 'world' is problematic since it casts foreign writers as somehow 'other.' Anglophone writers are beyond categorisation, which seems absurd. A very Euro-centric category which has overtones of imperialism.
'Comparative Literature' is an academic discipline used to analyse linguistic differences between writers from different countries, in addition to the usual critical perspectives from an English course. A useful discipline which not only broadens out from national barries but also draws from several other disciplines not commonly associated with literature.
So what is 'Cosmopolitan Literature' and how does it differ from the aforementioned categories. Cosmopolitan Literature holds that national borders are superflous and that there is a universal consciousness we all experience. This consciousness should be portrayed in literature, instead of relying on a parochial attitude of just representing the cultural mores of one's local society. It holds that literary styles developed from certain cultures can be freely adapted from others. A truly successful 'cosmopolitan' writer is one whom you cannot tie to a specific national canon.
Who eludes this category? Since when is Jorge Luis Borges Argentinean, for instance? The pampas appear in several stories, but his writing is more European than anything else. Although Conrad is called English because he wrote in the language, he wrote a novel set in Russia and novels like Nostromo are set abroad and populated by people from different nationalities. Is Roberto Bolano Chilean or Mexican or Spanish? The stamp of a true cosmopolitan writer is that he defies being placed in a cultural pigeonhole. This is because he avoids the style characterised by his local school and because he engages with different cultures.