Many many poor people came to this country and became a success.
I would argue that the efforts of the poor more often make other people a success, but I'm not negating your point.
We need more people one way or the other if we want to pay our bills and stay competitive with China through the rest of this century. China has a billion people and a one party system that, despite its displeasing qualities, can get shit done.
We need more people participating in our economy, not less.