For Hildegard, rulers who blatantly violate the virtuous example set by Christ lose their authority to rule. Following from that, an unvirtuous ruler would necessarily fail to be a right authority that can legitimately wage war.
The fact that Americans have shifted their focus back to domestic concerns isn’t abnormal or un-American. It is the predictable resurgence of the two domestically focused schools of the American foreign policy tradition.
In “The Education of an Idealist,” Samantha Power comes across as a compassionate person with generous impulses. These attributes cannot by themselves determine policy on the question of humanitarian interventions.