Sounds like HW to me as well, but since I am responsible for dozens students who don't read their syllabi, it won't hurt to try t help one more.
It's true that traditional theories are highly statist and tend to elevate the state as the primary actor in international relations, while downplaying others. Realism(s), most liberal theories, institutionalist theories are guilty of this. However, there is no theoretical limitation to analyzing non-state actors in the context of these paradigms as long as you are able to do so in a manner that would be consistent with its assumptions. Non-state actors (such as ISIS) are not as big a challenge to theory as is often assumed.
For example, Realism focuses on the impact of the system (anarchy) on balancing outcomes based on the structure of the system (i.e. polarity). You might say, oh but this is about states' foreign policies and alignment preferences. Moreover, states are functionally undifferentiated and their unique characteristics don't matter for such analyses. However, there is nothing stopping you from looking at another level of analysis and highlighting different aspects of the struggle for power under anarchy. You could say that states are but one type of political organization we encounter in anarchic systems, but the logic of survival dictates that all political units, from dynastic competitors to terrorist organizations have the same goal: survival. In this sense, ISIS is not very unique. Furthermore, Realists and liberals are more than capable of dis-aggregating the state in order to examine specific phenomena such as elites coalitions, interest groups, corporations, and state/society conflicts. ISIS could easily be understood as a group that rejects the present domestic and international status quo and can be treated as a transnational insurgency. Not only that, but mainstream IR theory has some of the tools needed to address ISIS. Realist theories can observe the phenomenon in the context of third world security dilemmas (see: Stephen David), utilization of non-state actors by states as a weapon of the weak (literature on state sponsoring of terrorism), or state formation/building (Tilly and countless others). Liberal theories can consider the role of economics, ideology, transnational flows of people and ideas etc. to explain the rise and success of ISIS etc.
I think the real problem is that some people read hyper-globalist drivel and all these hipster arguments about "the world falling apart and how the state and realism are dead!! etc." and think they can claim that statist conceptions of international politics are quaint and the state is destined to disappear and so on. States are not going anywhere; they are here to stay.
IS certainly challenges the westphalian order which is central to some traditional IR theories.
We aren't even in a Westphalian order. The modern international system with strong sovereignty truly emerged in the 19th century. But more importantly, IS is attempting to build a state. A state is state is a state. Not very "anti-Westphalian", if you ask me.
But traditional IR theories are shit anyway
Realism and the English School are rather excellent. I don't care much for Liberalism, which is composed of several equally degenerate research paradigms ('Realism-plus' aka institutionalism and hegemonic stability theories, Derpocratic Peace Theory, and we-stole-our-assumptions-from-soft-constructivists-like-Barnett-and-Wendt-etc-liberalism)
"It is a dangerous thing to be a Machiavelli. It is a disastrous thing to be a Machiavelli without virtū."
- Hans J. Morgenthau