Well, the restrictions on immigration do make it hard for highly skilled workers to come here. Many in the tech industry oppose Trump's policies for exactly those reasons. Whether those "white collar workers" would vote republican is questionable; they likely oppose racism that discriminates against them, so it would be hard to accept Trump policies.
The point of being American is that people are treated as equal under the law. You should welcome immigrants so that more people are treated equally, with human dignity, as Catholicism teaches. Where the USA departs from "all men are created equal" we should fight so that all are treated equally. And we should support other countries, like Mexico, so that they offer the same respect.