I agree that the cultures are too different, but it will settle over several generations. I am not saying that this is a good solution or even any solution or that a country should do this.

Just know that if you look around you most people do not look exactly like you, there are different eye colors and different hair colors and maybe there are even different skin colors that you do not mind. These people also came from different places several generations ago, yet you all get along fine now. These immigration problems are over the course of 100 years or so only temporary, if everybody on earth only existed out of people that tried to live of others we would have died out long ago.

This is why i say that even worst type mass immigration will have a tipping point where people will have to get along or there will be nothing to live off anymore. I think this usually happens within 2-3 generations.

Immigration is also broader than mass import of 3rd world countries. Look for example at the UAE, their immigration comes from mostly western countries. It just depends on the point of view and i understand your pov is immigration == poor people coming to your town living off of western social systems, which is bad for sure, definitely in the short term and definitely too many.