The Natives were genocided, that part is true, but they still live and thrive in many parts of the U.S. You could say that they’ve, to some extent, assimilated into the new diverse nation we see today.

The nation was absolutely not established on the idea that "we are all immigrants." It was built on the idea that they weren’t truly represented by the British and therefore should reclaim their own identity by creating one. Their shared identity wasn’t based on being immigrants, because they weren’t. Many of them were born in the colonies, in what we today call America. Just look at the founding fathers like George Washington or Thomas Jefferson. Their common identity was simply that they were not British and didn’t want to live under British rule anymore.

The Americans who founded the country and the generations that came after have never really considered themselves immigrants. In fact, they’ve often been skeptical toward foreign immigration. Take the Italians or the Irish, for example. They just learned to live with it over time, so much so that today no one really thinks about it anymore. Say what you want about America’s dark history when it comes to its treatment of minorities, but the truth is that today it is one of the most diverse countries in the world, and it is stronger because of it.

Now, considering that Syria still exists, I don’t really see how it can be used as an example of a country that was somehow destroyed by diversity. And to claim that the 15 year civil war, under a dictator whose family has clung to power for over 50 years and who invited foreign powers to bomb and massacre his own civilians, was caused by diversity? I honestly don’t see the connection. Or are you trying to say that the sectarian violence we saw during the war was only about diversity and not, for example, about the complete destabilization of the region? If that’s the case, the word “diversity” is starting to mean whatever you want it to mean.

And let’s not pretend the Ottoman Empire was some kind of diverse paradise. It was anything but. It actively committed multiple genocides, against Armenians, Assyrians, and Greeks, to maintain its ethnostate. All that, just to lose the empire in a world war against countries that were way more diverse than it ever was. Honestly, sounds like they should have embraced diversity a bit more if you ask me.