A footnote on cultural assimilation, or the lack thereof.
Simply put - immigration should also mean the assimilation of values. When you leave one country to live in another, there must be some reason. If the you move to another country to gain a better life, the assumption must be that you will largely absorb the values and practices of your new country.
Civilization is not buildings or structures. Civilization is not laws written in books, or words printed on paper. Civilization is a set of ideas, beliefs, and practices - and as such only exists in the minds of the people.
If one place in the world makes a better place to live, then immigants must be expected to absorb the ideas and practices (perhaps not all, but a significant part) of that better place. To preserve the “civilization” of that place, there is no other choice.