Revelation 7:9 After this I beheld, and, lo, a great multitude, which no man could number, of all nations, and kindreds, and people, and tongues, stood before the throne, and before the Lamb, clothed with white robes, and palms in their hands;

God does celebrate the diversity of peoples and kindreds on the earth. John the Revelator sees this in the celebration before the throne of Jesus Christ, The Lamb of God.

The curse falls on the mixed children for the actions of parents not sticking to their own racial lineage as these misceginated children struggle to identify with a group at the playground, the bus stop, etc.

God will sort it some day, as His ways are higher than ours.