So the prince with mouse ears wants to create a country without war, and he has a brilliant plan to do this: Unite everyone under the same banner. Non-violently, of course.
And then Roland, the president of the United States who was isekai'd into this fantasy land, says "yes, and" and hatches a plan to have every one of the warring factions sign a treaty called the Declaration of Interdependence.
All I'm saying is that even Robb Stark had a better grasp on the politics of a medieval society than these dweebs.