This seems to be the theme of the parable of the sheep and the goats in Matt. 25. Who are the brethren of Jesus? He Himself told us, on an occasion when his mother and kinfolk showed up with the strait jacket and butterfly nets: "Who is my mother? Who are my brethren? These who hear and keep the word of God!" IOW, even the closest physical ties are as nothing compared to the commonality of faith.
The nations that hospitably recieve the messangers of the gospel open the doors to heaven's blessings. When you read the stories of national conversions, the dominant note is great joy. (I'm thinking in particular of Kiev in 988.)
Of course following God yields blessings. Even atheists following God's laws would experience a measure of sowing and reaping blessing.