God does deal with Nations throughout the Old Testament, as well as on an individual basis, but are not made righteous through good works, only true faith produces true works. Any need of help and love done to members of The Body of Christ, sheep caring for lambs in Christ's fold is done as unto Christ, receive their reward in that Day when Christ comes in His Glory, at the end of the Tribulation. When Jesus speaks of unbelief in His teachings it is a warning against unbelief to try and save people from an agonising eternal separation. The underlying principle is at Jesus' Second Coming to gather out of His Kingdom all things that cause stumbling and iniquity, shall be removed. The inner nature and character of all are laid open and bare before the Perfect Judge.
Eternal destinies are at stake.
Everlasting torment was prepared for the devil and his angels. God desires all that would be blessed, Hell was not intended for people. The people have willingly chosen to refuse the Life offered. This judgement reminds all, that what affects Christ's people, affects Him. There are two symbols, two groups of people and two destinies.