How is the number of foreigners already in a country irrelevant, when deciding whether to admit more? From the perspective of the host country, migrants or refu

How is the number of foreigners already in a country irrelevant, when deciding whether to admit more? From the perspective of the host country, migrants or refugees makes no difference. And it's 1 million in one year, but 5 million since 2008. Unlike with Colombia, almost none are from neighboring countries. That's counting only refugees, not total immigrants: https://en.wikipedia.org/wiki/European_migrant_crisis#Asylum_applications https://en.wikipedia.org/wiki/European_migrant_crisis#Asylum... Given these numbers, is there any amount of immigrants the EU/US would have to accept, to be considered sufficient?