One is a political system, the other an economic system.
You need government to implement socialism, which makes it a political system.
Nationalism always trumps internationalism in its many forms: ie Communism, Socialism, Globalism,World Empires, Universalism, Islamic Umma and even Universal Catholic World Church. Nationalism is more linked to ancient tribalism and can be understood by the masses—The Internationalism is more academic and hard to imagine (That’s why it fails in the long run)