Generally, I consider something to be dystopian if it is making negative assumptions about the future that are rooted in speculative fiction. These are more like science fiction, fantasy, or geopolitical.

I consider something utopian when it is unrealistic and glossing over aspects that are impossible or poorly premised while presenting them as positive.

An example of dystopian would be the Terminator films or most films and books about AI. These fall into a trope of the machine gods. These are no more than a retelling of a pantheon like mythos of supernatural gods. The issues of future AI are unrelated to this mythos. They are also based on the fallacy of dominance caused extinction. By this logic Earth is a monoculture. These conceptual abstractions are dystopian because they are making stupid handwaving assumptions that result in a dark and grim setting.

Depicting the messiness of reality does not mean a fictional story is either dystopian or utopian.

An example of a utopia is something like a biblical paradise. It is premised on brutal authoritarianism that lacks any objective nuances about the true diversity of life and opinions. It is glossing over the real differences in what people want and expect out of life in an idealized story arc that harms a lot of people. When these people are sidelined as irrelevant, the true underlying dystopian reality comes into view. Utopia is always a story of propaganda-like perfection masking a terror that lies beneath.

One can paint such abstractions on almost any story. These are not really genera even if someone calls them such.

You mentioned your story involves massive geopolitical upheaval. This concept could be painted as dystopian depending on how you write it. Throughout history there were many underlying reasons for changes. Like in the era of Alexander the Great, the conquests of the Macedonians in that age were more due to advances in equipment and a professionally trained army in an era that primarily consisted of less formal city states and small raiding parties. The era of the Romans was mostly the beginnings of broader social cohesion and coalitions of regions. The Great War and WW2 was the era of solidifying global boarders and the role of imperialism. If you are proposing a new era of evolving change, the reason for that change and why that change is a form of evolving progress in a geopolitical sense is important if you would like to abstract a label of utopian or dystopian. Otherwise it sounds like “war fiction” IMO.