America does NOT have a "blood and soil" culture as they do in Japan. It never has.
1. I have very good, long time friends in Sweden. Sweden backed off allowing a lot of Mulsims quite a while ago. They learned their lesson. So, according to my friends (doctors, engineers, teachers, etc.) and their families, Sweden ISN'T overrun with Muslims. It never really was. When 500 Muslims were present it SEEMED like more because they (Turks, actually) were so very, very, very different from Swedes and stood out like sore (very sore) thumbs.
I was just in Germany. I was there for a month and visited about 10 cities and spoke with tons of people. I kept asking, "Where are all the Muslims? I had heard....."
Well, Germany, with its 82 million people, isn't overrun either. It's hype, all hype, probably media hype.
You view of Germany and Sweden is incorrect, but understandable, considering the huge volume of U.S. hate-filled anti-Arab/Muslim/Palestinian rhetoric that has been pouring out of the blogs, magazines and Internet for the past several years. I don't know about Norway and Denmark. Maybe THEY are "overrun."
They do preserve their culture because in those countries they still speak, read, write and post signs in THEIR language. They DON'T worship at the altar of diversity. They don't hate themselves, their history, culture, traditions or religion the way so many self-hating American leftists, multiculturalists, secularists and athiests do.
2. True. MOST countries of the world ARE NOT based on immigrants, like we are and MOST counties of the world ARE homogeneous and work hard at preserving what they believe to be their own, usually superior-to-others, culture. We are one of the few countries on the planet that IS immigrant based. We are, by nature, multi-ethnic, NOT homogeneous, and therefore prone to the problems of NOT being homogeneous. This WAS bound to happen to us when we got so many millions of non-European, non-Christian immigrants.