I bet the natives and indigenous people of Latin America, North America and Australia are looking at these migration numbers and thinking no wonder you're so terrified because you saw what your unregulated migration did to our nations and way of life.
Even Europe had that happen.
Look at the British Isles. Only the very far places are still Celtic (Wales, Ireland, and Scotland), and even the Celts weren't native to the area. Other than some vague stuff about the Picts, we don't know much about the pre-Celtic inhabitants of it., other than they built stonehenge and such.
Or Spain. You have the Basque people still hanging on, but they've had to deal with Celts, then Romans, then Moors.
Ort the Scandinavian countries. While we commonly think they have always been "Nordic", the original inhabitants of the region were Sami. They were colonized and displaced by various Germanic tribes (who then invaded other parts of the world as Vikings or Normans, including France, England, and Ireland).
And the Middle East is just as bad. Look at the Copts in Egypt, the Yezidis in Iraq, the Zoroastrians in Iran. All used to be fairly dominant cultures in their lands, but were displaced by foreign colonizers. And look at the Kurds who have had their land, Kurdistan, split up with parts into 3 different countries, one of which, Turkey, really only existed in 1492 when the Byzantine Empire was conquered. (And largely unnoticed, the Turks are still warring with the Kurds)
It's just how the world works. Sometimes you end up with something better, like arguably in England where they forged an identity from all the diverse people who lived there, Celts, Romans, Germans (Angles/Saxons/Jutes), Normans, Danes, then later Asian Indians and assorted others from their empire.
But even so, it generally comes at the loss of a culture. It's essentially a form of darwinism.