Just to turn this discussion on its head in a friendly way...
Those Spanish, French, and English immigrants really were a cancer (or should I say "small, 'pox'")to Native American societies when they refused to assimilate as well.
I guess the same thing could be said for all those Europeans who refused to assimilate in Africa; SE Asia; Australia; etc. during those Ages of Imperialism.
Damn that "White man's burden" principle.
(Please don't delete because this post may be considered "liberal" in a military hobby dominated by folks who tend to lean slightly to heavily to the "right." It is in the spirit of an alternative perspective. Take it with the humor/truthiness that is intended.
There are real issues with immigration of which the original post is just one.)