Earlier quoted context omitted.
I don't think you're thinking of the historical details to say that in such a blase manner. The path to integration went through periods much more violent and contentious than anything we see today.
I'm aware of how immigrants were treated back then and I'm not condoning it. That still doesn't change the fact that they came from cultures that IMO were quite compatible with the USAs considering their common origin and values. I think the current situation in Europe, and other instances of mass migration in history, demonstrate that not all cultures are compatible with each other
America’s secret superpower is the ability to assimilate pretty much any people within four generations give or take