We do not WANT to block illegal aliens.
They are the salvation of the Social Security system.
As Americans age and retire, there are fewer and fewer young workers with paychecks to raid for SS taxes. How to stave off disaster? Let the Mexican come, by the millions, and let 'em work any jobs they want. There won't be enough natural-born Americans to fill 'em anyway. Abortion and driven women pursuing careers have ensured that the birthrate has not kept pace with the death rate of US citizens for a couple of decades now. If it were not for the Mexicans flowing in, we'd be facing a demographic catastrophe. Viva Mexico!
You have eloquently grasped a BIG part of the immigration issue. The rest is that the immigrants are coming here for the perfectly Republican ambition of earning a real living to support their families and NOT so that son Pablo can "marry" James McGreevey in New Jersey or Massachusetts or so that daughter Maria can abort their grandchildren, as in both cases the Demonrats would prefer. So far, 12 million Mexicans are trying to cover the job obligations that might have been covered by for 47 million "Roe vs. Wade" slaughtered American babies.