Blessed is the nation whose God is the LORD; And the people whom He has chosen for His own inheritance.
Now therefore, if you will obey My voice indeed, and keep My covenant, then you shall be a peculiar treasure unto Me above all people: for all the earth is Mine. -- Exodus 19:5
But you are a chosen generation, a royal priesthood, a holy nation, a peculiar people; that you should show forth the praises of Him who has called you out of darkness into Him marvelous light. --1 Peter 2:9
While there are many nations on this earth, the only nation that matters is the 'holy nation'. It is a collective group of people who choose God as LORD, who call upon His name, as Seth did way back in Genesis 5:26 all the way up to today.
Romans 10:13 For whosoever shall call upon the name of the LORD shall be saved.
And just whom does God choose for His own inheritance? Those who obey His voice when He speaks and keep or follow His Word. As Jesus said when He began to minister to the people (after overcoming temptation in the wilderness), firstly "Repent, for the kingdom of heaven is at hand." And secondly, "Follow Me and I will make you fishers of men."
First, we repent and believe, then we lead others to Jesus Christ that they, too, may repent and believe and follow. That's how a holy nation is built up. That's the generation whom God has chosen for His inheritance.
I am part of this generation. Are you? Do you want to be?