The first half is true, because roads are a key instrument of military invasions, and that's how empires rise.
The second half is true in that all empires of any scale build walls regardless of whether they're rising or declining. An empire with no walls is an empire that belongs to someone else.
But neither of those seems like an especially deep or compelling point.
> "Good fences make good neighbors" experienced early retirement. In its place came the untested phrase, "Build bridges, not walls." If nothing else, the new slogan seemed designed to give military historians fits. Throughout history, bridge building had been recognized as an act of aggression.
( https://www.amazon.com/dp/1501172700/ )