@Germlat,
I am not dancing around the issue at all. Here is the problem.
For you demographics is important to the point that you are using the words like "threaten" and "cultural instability" because of a change in ethnic background. The fact France was a colonial power that made economic decisions which brought people into France... and that this demographic change is part of the natural course of French history doesn't seem to matter to you.
To me, the moral values Democracy are important. Equality and liberty are bedrock values of our society. The American story is the story of extending rights to more people as we have grown as a society and taken in people of more cultures.
What would I do? Simple, I would hold to our values; our American values (with the caveat that perhaps the French don't have the same values). Our values of fairness and liberty and equality are important. Demographics aren't.
A key part of our immigration law from the early 1900's to 1965 was called the "Asian exclusion Act". It shouldn't surprise you that this law was designed to make sure that there were never too many Asians around... because we all know the threat that Asians pose to American culture.
Of course when we repealed the Asian Exclusion law in 1965... it did in fact mean that there were a lot more Asians becoming part of American society and there are lots more Asians around now than there would have been.
So What? Immigration policy based on demographics is deeply racist. They go against the core values of our country.
I am not dancing around any issue. I am arguing that immigration policy based on ethnicity goes against the values of liberty, fairness and equality.