There is a definite impact to a society when they open up to outside cultures. Countries who don't have a history of large scale immigration face challenges to their identity, and cultural strength, especially when immigrants don't desire to integrate with the culture they migrated to. The citizens have to learn new skills, interacting with people that are different from them, and need to learn acceptance and tolerance. Those are valuable skills to learn, but it's dishonest to pretend that immigration doesn't have any impact on the host country. Certain European countries have been getting a master class on the challenges that mass immigration poses to their unified cultural identity. I'm from the United States, so I'm no stranger to immigration, but I recognize how there would be an adjustment period for those who are.