Zero immigration policy would shoot ourselves in the foot. We need engineers, doctors, technicians and American citizens are not graduating with those degrees in sufficient numbers to fill the positions needed. Unrestricted immigration and America will be overwhelmed. Zero immigration and America will not be able to grow or soon function. We need a slow growth immigration policy that favors occupations we need and allows time for integration and assimilation into American culture.
First zero immigration allows for a few thousands of immigrants for various reasons, as far as needing skilled help because America can’t produce it’s own, thank immigration for that.
America was doing fine a 120 million people ago. The United States is behind only China and India in population.
We need to end immigration, in your post you wanted to end illegal immigration and made a point of wanting our continued flood of legal immigrants.