Another user already explained world systems theory, but there's also the school of global historical materialism, that analyses the relationship and structure of the imperial core/triad and the periphery/global south. Samir Amin was a leading figure in that, he also coined the term "Eurocentrism". You can find quite a few recordings of his lectures for free on YouTube, or pirate his books (he's dead now, so it's not like he'd get the money anyways).