> ...They recognize that individual immigrants can be fine but the large-scale flow of immigrants can create undesirable changes

You should also consider the other side of the equation, which is that immigration is the only thing that's keeping the US workforce and total population growing.

The size of the workforce and overall population has real economic, fiscal and quality of life impacts that every American feels on a daily basis and there's a very strong argument to be made that if your interest is in maintaining US wealth and "strength" globally, you don't want to become Japan, South Korea, Italy or Germany.

This is not to say that immigration policy should be made thoughtlessly or recklessly, but I rarely see the staunchest immigration opponents mentioning the stark demographic reality that faces the country.