(This has nothing to do with nation-states I just love Christmas)
Following the Peace of Westphalia (1648) the conventional approach to global politics has been state centric, i.e. the state is the most prominent actor on the world stage. However, one of the by products of intensified globlisation is a proliferation of non-state actors. These non-state actors (be they NGOs, TNCs, or other non-state bodies) now exert a varying degree of influence in the global system. Liberals see globalisation as the main weakener of state sovereignty (and therefore the significance of states). They prefer a mixed-actor model as opposed to states as the only actors. Realists on the other hand emphasis the role of the state in global politics in that they are the fundamental building blocks of the system. Furthermore, there is an argument for the middle ground, in that the role of nation-states in global politics has changed- but this does not necessarily mean the power of states has become redundant.
The growth of international organisations and the move towards regionalism can be seen as weakening the importance of nation-states. For example, the trend towards global governance has seen elements of supernationalism in some organisations like the EU. The debate as to whether the EU has eroded the sovereignty of it's member states has been exhausted, one conclusion to draw from it is that while the EU does appear to be a higher authority than nation states (e.g. UK Parliament cannot pass any statute that conflicts with the existing EU laws as seen in the 1990 Factortame Case). Having said that, member states reserve the right the exit the EU- we may very well see a vote for 'Brexit' in the upcoming EU referendum. This surely indicates that, ultimately, states are the predominant actors in the political arena as they choose to be a part of these organisations to boost their own power by through pooling.
The growth of TNC's can also seen to be a threat to the dominant position of nation-states in global politics. For example, of the 100 largest economies in the world, 51 are corporations; only 49 are countries. Wal-Mart (12th biggest) is bigger than 161 countries, including Israel, Poland, and Greece. Naturally, these corporations have a sizable influence over states, as Susan Strange put it "where states were once masters of markets, now it is the markets which, on many issues, are the masters over the governments of states". Although it can be argued that states are still important in that they provide legal and social order in which these corporations can operate.
While it may seem as though the status of states has reduced in global politics, it can be seen that they have merely changed in nature. Instead of a billiboard model of states all competing in their own interests, we see a new multilateral era where states recognize the benefits of working within an international organisation- for example national interest has become international interest, such as global climate change or the global terror threat. Furthermore, the success of supernationalism (i.e. states surrendering sovereignty to a central authority) is, arguably, grossly exaggerated as Europe is the only region that follows this concept.