"kingdom" here refers to the people in it. This can also be stated in active form. Alternate translation: "If people of a kingdom fight among themselves, they will destroy their kingdom" (See: [[rc://en/ta/man/jit/figs-metonymy]] and [[rc://en/ta/man/jit/figs-activepassive]])
Here "house" refers to a family. Alternate translation: "if family members fight each other, they will ruin their family" (See: [[rc://en/ta/man/jit/figs-metonymy]])
"crashes down and is destroyed." This image of the house collapsing refers to the destruction of a family when the members fight each other. (See: [[rc://en/ta/man/jit/figs-metaphor]])