it'll make a big difference because they will have to quit their jobs, go home, and wait - it's not like their quick 2-week trips home for the holidays
But it won't make any difference in the long run. The losers who now blame Mexicans for their inability to keep a job still won't be able to keep a job.
The people who are dependable, have a good attitudes and take pride in having the job will continue to be promoted while the sorry little whining malcontents will continue to get fired. When government tries to force businesses to hire union bad employees, the businesses will find some way around it or relocate to areas with non-hostile governments.