Re: "...details a plan to build a wall between the United States and Mexico." (@ Boltar)
"God, not this tired old argument again."
Which argument? That the Big Wall will only worsen things? I'd like to hear your counter-argument.
Fact is, the US govt. seems to agree with me, as they are doing zilch -aside from some hand waving - regarding the issue. Which measures should they take, you'll ask?
First the switch: lots and lots of surprise inspections in the areas where illegal workers are more common, e.g. construction, agriculture, domestic service... . with big fines/prison terms for illegal employers. Remember, in most cases the "illegals" are the victims here.
Then the carrot: helping the development of the countries where the illegals originate, both economically and politically, so as to prevent people from wanting to escape the terrible conditions in said countries.
Instead, what the US does is spending trillions in stopping perhaps a 20% of illegal immigrants -so as to appease the voters-, milking the origin countries off most of their natural riches and capital, and directly promoting criminal/dodgy/corrupt regimes in said countries to facilitate the above said plundering of natural resources.
I think that the main reason for this sad state of affairs is that in the US the main objective is private profit. The current status quo allows the government to put pressure on salaries -with all the consequences you list in your comment and then some more- while keeping the public happy " 'cause something is being done".
In short: the US economy is designed to depend on very low wages/living standards for a big % of the population, and, sadly this won't change by itself, even if you reduce illegal immigration to zero, as other means will be used to keep salaries down (e.g. more economic meltdowns).