I know I'm pages behind here (so apologies if this is already covered -- I'll come back and edit), but while I don't dispute this I wonder whether a factor in this is the illegal immigrants can/will work illegal jobs -- meaning paid under the table, below minimum wage, not paying into FICA/unemployement insurance, etc.
The government has killed many jobs by making the roles too expensive to legally hire. Law-abiding employers and workers aren't willing to take the risk of getting caught working illegally and the job itself can't exist legally as the gov't mandaded cost is higher than the value.