Do two walk together, Unless they have agreed?
One of the big things in this whole passage is Amos' view of history, not as the accidental and opportunistic deployment of peoples upon the earth, but as a "controlled" entity, subject, absolutely to the will of God. Nations rise and fall by God's will only, wicked nations being used for a season to punish the righteous, but themselves being quickly liquidated when their sins have gone beyond that hidden boundary that separates God's mercy from his wrath.