It's not just about Christian pacifism, or nonresistance. It's -more to the point- to what and to whom we belong. God is our King. And we in Jesus are part of the kingdom of God made known and spelled out in the good news/gospel of Jesus.
So it's an identity issue. And then the question comes just how much, or to what extent we can be identified with our various nations, as the new Israel scattered throughout the earth. That is not an easy question, and both individual Christians, as well as churches will vary on their answers, or practice, even within the peace churches.
Well said. As Christians our first loyalty is always to the King of kings. He cites Bonhoeffer as a good example of that.