We have a very generous legal immigration system to offset a stagnant population, and if need be we can increase mechanization in many sectors of the economy, including agriculture.
Those who want massive illegal immigration are either naive or are profiting somehow off of the cheap, compliant labor they're pushing onto us. And we are not fooled in the least by the Wall St. Journal/open borders rhetoric of doom and gloom if the borders are closed.
I agree.
What I have been saying is that illegal immigration is, simply speaking, supply fulfilling demand. Those who would "close the border" are attempting to resolve the issue by artificially curtailing supply. As any student of history can tell you, this will simply not work.
I would also suggest to you that Japan is not a valid comparison for many reasons, not the least of which being, the Japanese are extremely intolerant of gaijin, people not Japanese. Their society will pay almost any price not to have to associate with outsiders (be they Asian or European).
Further, I will stipulate that most people who oppose open borders with Mexico and/or South America do so for the same reason the Japanese do; intolerance, bigotry and prejudice. Several of the recent respondents to this thread strongest argument against mestizo immigration is that they take welfare destined for "real" Americans, live in squalor, fill our prisons, and that their neighborhoods are crime-ridden.
Lastly, cheap, compliant, labor is an important constituent to a strong economy. I want a cook, maid and gardener that will work hard for low pay. It would help if our "Masters" in Washington would recind minimum wage laws but in the interim I can understand why illegal immigrants are desirable.