An awful lot depends on how you define things...
"Immigrant" for example. There are people that argue that we are a nation of immigrants, and that is true, not just for our nation, but for virtually all nations, if you go back far enough.
Other than a few stone age tribes in ultra remote portions of the world, ALL nations existing today have been built from sucessive immigrations. Usually at the point of a sword, lance, spear, or arrow. Choose any country you wish, and go back in their history and you will find at least one example of "indigenous" peoples being forced out or slaughtered, or, at best, absorbed into the culture of the invaders.
Whether or not a people are "native" to any region is simply a matter of the time scale you use when making the judgement. The American Indian, now called "Native Americans" (a term I detest by the way) came from somewhere else. At least that is what science teaches today. To me, "native Americans" are all those, like myself, that were born in the US, no matter where their ancestors came from, or how long ago it was, last week, or 3,000 years ago shouldn't matter. But to many, it does.
When we "own" something that really cannot be owned, like land, we get posessive about it. This is the natural historical state of man. We come from tribal groups, and other tribal groups were our competitors for the resources that kept us alive. In many languages the words for stanger and enemy have a common root. And the reason is that historically, they usually were the same thing.
One reason so many are upset with the immigration problem of today is that unlike the earlier mass immigrations from Europe, the immigration from south of the border is not making any great attempt to assimilate into our general culture. And because of that, our culture is "diversifying", because there is money to be made from the hispanic immigrants. Mexican Spanish is the de facto second language of the western US, and making great inroads in the eastern states as well. And we are allowing, and even encouraging this, because of our own greed.
Previous generation of immigrants, (mostly) from Europe worked hard at becoming Americans. Grandpa and grandma may barely speak English, but Mom and Dad do pretty well, and junior and sis barely speak the old country language. Old country cultural celebrations were private things, done at home, or in local community centers. Sure, we had ethnic neighborhoods, like Chinatown, or Little Italy, etc. but each succeeding generation was more "American" than the previous one.
We don't see the "hispanics" doing that. They are seen as refusing to become Americans, keeping their language, and their culture, separate and apart from the general "American" one. Previous immigrant generations took great pride in who they were, and where they came from, but they also took even greater pride in becoming Americans. The hispanics take great pride in who they are, and where they comae from, but they, as a group, don't seem to give a rats ass about becoming Americans. Many individuals do, but as a group, they don't give many of us that impression. And the admittedly racist hispanic groups agitating for turning over portions of the US to their rule (Aztlan) don't do anything to change this impression.
The seeming unwillingness to assimilate, to learn English, to become what we would recognize as "good" Americans creates resentment, intensifying the natural distrust of "foreigners".
America worked very hard to win WW II. We changed our society drastically in order to do so. We put women in the workforce, in numbers unknown in previous history. We became the "Arsenal of Democracy", and when the war ended, that arsenal converted to consumer production. Our productive capacity, combined with our natural resources created a tide of prosperity that we are still riding on (although currently it seems to be an ebb tide). Our own success has brought us the problems we have today, and we must do something about them. Had we failed, it would have brought a different set of problems, but we didn't fail. The "Greatest Generation" and those following made the US into the mightiest nation in the history of man, and we have been generous.
But there comes a time when even the most generous and kind have no more left to give without paupering themselves, and many are wondering if that time isn't just around the corner, if not already upon us.