Factor price equalization due to trade and investment flows across economies would substantially reduce economic reasons for immigration to rich countries. (Trade and investment flows will not eliminate economic reasons for migration because if polities differ in total factor productivity due to political institutions, there can still be an advantage to migrating to a more efficient economy in a fully globalized world.) Therefore, if you are an American who is deeply concerned about immigration to the U.S. for cultural or political reasons, one way to encourage less immigration is to press for full trade and investment liberalization in this country and around the world.
Now, does opposition to immigration correlate positively or negatively with support for free trade and “outsourcing” in voters’ attitudes? In my experience, negatively.
Chalk this up to one more way in which politics is about symbolism rather than substance, due to public ignorance.