Ameribro here. I've hosted a German exchange kid. She was really, really worried about immigration and "preserving German culture". I pointed out to her that:
Culture is not a fixed thing, it's always drifting a little bit, with or without immigrants. That's why old people always complain about how different everything is.
Germany is actually younger than the US as a state by about a century, and contemporary Germany has really only existed since either the end of WW2 or the fall of the Soviet Union, depending on your view. (IMO, the collapse of East Germany is non-trivial. Her mom was an East German and described to us how they had an entirely separate culture with different groceries and everything and all that just vaporized into nothing when the wall fell, replaced with West German culture almost overnight). So, what does it really even mean to be defending German culture?
There's always hardship when a new group of people arrive, but over time you usually end up with something that's better than what you had before if you can learn to embrace it. US culture has, in spite of our issues with racism, tangibly benefitted from immigration over the centuries.
She wasn't receptive to it. A lot of Europeans who hold anti-immigratiom views insist that it's different for Europe when they have immigrants than it is for the US. I've yet to have one persuasively explain why that's true and not just whiny exceptionalism.