Are nation states still the most significant actors in global politics?

Political scientists have traditionally seen the nation state as being the key actor within global politics, in control of all interactions. This has generally been considered the case since the Peace of Westphalia in 1648 where the territorial sovereignty of states was recognised. Since then, wars have been conducted on a state on state level, normally over territorial disputes. Moreover, upon the conclusion of the war, up until perhaps the twentieth century, peace negotiations would see only state leaders participate, not international organisations or non-state actors.
However, with the rise of globalisation there has been a decrease in states' ability to act autonomously on the international stage. Transnational organisations have increasingly more influence within governments, undermining the states' ability to autonomously when making decisions. For example, Nissans' threats to move their UK bases abroad if the government was not seen to be supporting the EU was a major influencer in Cameron's pledge to stay within Europe, fearing British job losses. Furthermore, increasingly non-state actors are combatted in wars, state on state wars no longer the most common form of warfare. In Afghanistan US forces were not fighting an organised state, but rather a disparate guerrilla group in the form of the Taliban. Their force was shown by the amount of casualties the US suffered, showing that nation states no longer hold the strength on the international stage they used to.