Book 13 says the homeland is not finally America or Korea alone. The earth is meant to become one homeland under God. But it then makes a practical claim: the person able to create that homeland is the person who lives for the sake of the world.
That cuts against both private spirituality and narrow nationalism. A heavenly homeland is public enough to be a nation, yet wide enough that it cannot be built by loving only one’s own side.
The sermon hook is sharp: you do not build God’s country by shrinking your concern. You build it by widening your loyalty until the world starts to feel like your actual country.