It's really basic economics 101. If lower wages didn't hurt people's incomes, why have minimum wages? The typical pattern is that someone eventually gets into a position where they can hire people and from that point on they only hire their own kind. The workforce is taken over by immigrants and the poorest citizens of the host country suffer the most both from low wages and from lost jobs.
Also, if South America is really as bad as you say ... do we want people flooding in from there without proper checks? Isn't it all the more reason to vet people and protect the border with a proper ordered immigration and asylum process?
These countries are bad because they have abandoned law and order and allowed a free-for-all - the exact thing that civilized countries have to avoid and protect against.
A proper ordered process benefits legitimate immigrants the most and disadvantages the criminals and people smugglers. That anyone would want to support things that works opposite to that is simply mind boggling to me.
I am taking a basic course in economics, finishing first year at the University. You are correct in everything you say.
Perhaps in the past the idea was popular that immigrants that do the jobs nobody wants benefited America. But now with current research we know that's not true. If illegal immigrants weren't allowed to work in the jobs that nobody wants, like being a maid in plush motels, those corporations would have no choice but to raise the wages for those menial jobs and the LEGALLY unskilled labor force could take those jobs and climb their way out of poverty--LEGALLY.