I finally laid hands Immanuel Wallerstein's World System Analysis - An Introduction (thanks Steve) as I didn't want to read his trilogy as a way of introduction. I had a surprising grasp or pre-understanding of his theory through his essay collection The Decline of American Power and Arrighi's take on this concept. To recount again - in a simplified manner - the argument is that there is a dominant capitalist system in place ever since the 15th/16th century, which has as a goal the endless accumulation of capital. It moves in systemic cycles, moving from one hegemony to the next (with phase A seeing a rise in power, phase B a decline and a shift to a new hegemonic power). We obviously are in phase B of the American hegemony. Unlike most other social scientific attempts at explaining the world the state is not the unit of analysis, also the approach is unidisciplinary (no artificial separation of anthropology, economics, political science, sociology...) and finally the world system in this theory is of longue duree but not inevitable and endless.
Wallerstein's main point thus accordingly is that the 'endless' accumulation of capital is slowly coming to a natural end (because of an steady increase in taxes, external costs (environmental destruction for example) and the price of resources). I still am not too sure about this point, but am honestly for the time being more occupied with trying to tie this into my master thesis and how European emancipation of American dominance is tied into all this. Obviously, the general point is clear, American hegemony is dwindling (the twilight of the unipolar world to put it more poetic), Wallerstein's theory in the end is based too much on economic theory to be very useful in what I want to focus on in military and defense and security policy. I thus still need a logically and truly applicable theory to relate to the creation of the CFSP.
Nevertheless, if y'all ever become bored read through Wallerstein's introduction. Highly interesting and logical and applicable to some extent. Definitely food for thought and thus recommendable.