Precisely

The reason the United States, and every nation on Earth, restricts immigration, however, is precisely because we recognize that what is in the individual interest of a would-be immigrant is not necessarily in the interest of everyone else in the receiving country.

Look, I actually like immigrants a lot. Always have. During my brief time at Oklahoma State University--lo! those many moons ago--I was, as far as I knew, the only American member of the International Student Union. When I was in fast-food management, I hired a lot of immigrants. The ESL (English as a Second Language) class I teach is gearing up for the Fall semester, and of course, all the students are immigrants. I like immigrants. You gotta keep that in mind when I say that we must bear in mind that the purpose of immigration is not so much to better the lives of immigrants, but to improve the situation in our country! Any country, any government, must first look to the lives and prosperity of its own citizens. That is not to say that we should be unconcerned with the rest of the world, but to express the perfectly normal concept that there are priorities, and one's own country should come ahead of others, one's own citizens should come ahead of other countries' citizens.

That's how you shape and evaluate immigration policy, my friends...