I do not think it would eradicate our culture, it would just evolve into a different culture. Change is inevitable after all so I see no reason to fight this unification, a unified culture and "race" would probably make things better if it was possible, but I do not think we will ever get there. Culture is not only based on race, it is based on a lot of variables and we can always invent new ones. Even if we made everyone look more or less the same, people would find ways to alter their appearances and as such create artificial "races".

"That surface that tells the Heavens it hath an end, cannot persuade me I have any."