This is a lot to respond to here, so I won't be able to respond to all of these.

I didn't respond to valuing kin and culture since it wasn't clear what you meant by that. To be honest, it's still not totally clear - when you speak of culture being diluted, it sounds like you're talking about the influence that culture has on society as a whole? Or how many people in the society have that culture?

On the individual level, it seems like someone who grows up in a particular culture has that for life. People don't suddenly become Spanish, even if they live there from 30-50 years old. So in the course of your lifetime, your kin are still going to be there for you. But maybe you meant - if your kids don't have the same culture as yours. I don't totally understand why this would be a problem, unless they wanted to join some cult or something.

So if you meant preserving culture across generations, as you also mentioned, culture isn't static. Just look at how the culture of England changes from Tudor to Stuart, or from Victorian to Edwardian to modern era. You might say "Recent history is hard to compare to since influence from other countries has touched it and technology has changed so rapidly", but further back than that is not well documented, older histories written exclusively by government bureaucrats who have a specific view of culture. And even in recent histories - in those eras of England I mentioned - religions other than whatever was officially sanctioned at the time were violently held down, so even if you can say there was "A Culture" in England at the time, it was through violent force and fear of violent force that it was kept that way.

What's great about America is the ability to hold so many cultures and through democracy be pretty stable, but I don't know if there's ever been "an American culture". Even the founding story of America - escaping religious persecution - speaks to the horrors of enforcing cultural homogeny. What if, at Plymouth Rock, they met some Native American Nationalists? (Yeah of course there were some tribes of american inidians who attacked the colonists, and some who didn't) It's easy to blame changing culture on immigrants and outsiders because the world is opening up and so many people are moving around, but shifts happen within a single "culture", culture is not static even without an external force.

You speak of conflict, of efforts to colonize, and it's true that world history is almost constant warfare. We are currently in the third longest period of peace (and probably most peaceful)[0][1] in known history. We are also in the most accepting times of other cultures. You say that conflict happens across ethnic lines, but how can you explain the long period of peace happening during the time of most cultural cross pollination? The longest time of peace was the Pax Romana, when the Roman Empire explicitly let conquered nations keep their local cultures, and travel within the Empire was commonplace.

Do I want to preserve my culture through my kids? Yes. I teach them the importance of knowing where they came from. I bought books about my ancestor who was on the Mayflower and they're proud he was there for the first Thanksgiving. Mostly, I want them to be good people, and know that the older they get the less influence they will get from me, so I try to show them how to be empathetic, kind, strong willed, and when to know which to be, so no matter what beliefs they end up with they are coming at them from a good place.

And as for genes mirror geography - yeah - people didn't move around much before the airplane. It's pretty great that common people can travel the world. And as for personality traits being hereditary - I actually didn't know that and it's very interesting. I don't know how it relates to your overall argument, but biodiversity tends to be good for the whole ecosystem.

[0] https://qph.cf2.quoracdn.net/main-qimg-b26b8004884501d83fc8c...
[1] https://en.wikipedia.org/wiki/Long_Peace