Well, that is your opinion. I do not share it. If the troglodytes do not manage to kill off life on Earth, humans will become homogeneous as differences in DNA mingle and hybridize. Our current differences (outside of having some H. Neanderthalensis DNA in some people) are due to epigenetic reasons. Climates, geological differences in different regions, etc. affected genes but population is growing so quickly and we are interbreeding so quickly, those affectations to DNA are lagging more and more.
=)
That would depend upon what you would call "white culture", who you refer to as "our", and that your opinion that "our" social and political system is best is debatable. From my viewpoint, white culture is from Europe and it added difficulties that were previously non-existent to North America. Brown people from the ME are currently doing the same thing to the white people of Europe as well as to white people here (to a lesser degree).