It's true when you flood nations with different peoples akin to the fall of Babylon. There's no assimilation to a central culture so it's like oil in water. But your implication of people being unable adapt to another culture is just ignorant of human evolution and history (non-normies are capable). In the US, we had means to control the flow and force assimilation, it's just all the natural barriers are gone and the whole is now spoiled. Going back is now incredibly difficult. Divide and conquer can still apply to shattering a nation's monoculture that originally had people coming together for a common ideal.

It's true when you flood nations with different peoples akin to the fall of Babylon. There's no assimilation to a central culture like oil in water. But your implication of people being unable adapt to another culture is just ignorant of human evolution and history (non-normies are capable). In the US, we had means to control the flow and force assimilation, it's just all the natural barriers are gone and the whole is now spoiled. Going back is now incredibly difficult. Divide and conquer can still apply to shattering a nation's monoculture that originally had people coming together for a common ideal.