“Should Christians respect borders?”
Borders are neither essentially good nor bad: they simply tell us where one state’s authority ends and the next one’s begins. In principle at least, borders are morally neutral.
In fact, God himself was behind the original borders between the nations. As Moses put it, “When the Most High gave to the nations their inheritance, when he divided mankind, he fixed the borders of the peoples.” This is a reference to the fallout from the judgment at the tower of Babel, when the Lord dispersed mankind over the face of the earth.