consider that the same thing happens without immigration
No, the same thing doesn't happen. Civil wars are actually very rare these days. With shitload of foreigners who want to keep their culture it means problems. This is noticed in all countries who have a big number of foreigners. I don't want Finland to make the exact same mistake that Sweden made. Now there are areas (ghettos in other word) in some towns in Sweden where even police can't operate, because they are afraid. Foreigners just suck that way, they become criminals easily. Maybe that's the reason why their own countries also suck (like Somalia, one of the worst places on earth).
Well, you have a point.
Inmigration *does* lead to problems, but the problem isn't inmigration
per se, or the inmigrants in themselves.
I'd say that the problems stem from three things:
1: Illegal inmigration
2: The lack of method when taking formal, lawful inmigrants.
3: Unwillingness of inmigrants to adapt to some aspects of culture
4: Probably the root of all problems, that most inmigrants were shit poor in their homeland and inmigration is a last resort action, actually to send money to their family.
Okay, here in Spain we had a relatively recent (in the seventies or something like that) wave of
emigration. Mostly to Germany, but also to Switzerland. Most people that emigrated there were guys and girls in the prime of their youth who seized an opportunity to send money to their families back here because those weren't exactly golden times here.
Bear in mind that I'm talking about the archetypal example, which is quite common, but surely there were differing cases.
Those young people were separated from their families, working in a country about which they knew next to nothing, and used to live in barracks next to the factories they worked at. That is nothing to sneeze at.
A lot of them returned eventually, but some of them stayed there and could very well be around the third generation of spanish-descended germans. Others returned on the second generations - the emigrants came back with their german-speaking children.
The problems arise when people who move to another country in dire need of work are either gobbled up by inmigration mafias, or refuse / are unable to adapt to the uses and customs of their new environment. When in rome, you know, do as romans do.
I don't think that first-generation inmigrants settle the issue, it's their kinds and grankids with whom you check if the process is going well. If their kids speak both languages and aren't out of place in society or causing problems, I'd say it's okay.