Thus a crew of Americans (of all stripes) with a bit of education and experience have to bid higher on jobs and don't get them. Illegals with no language (could prove dangerous on the job), no background (could be a murderer on your crew), no education (no quick geometrical calculations) crowd out young apprentices who would be better qualified to do a better job.
My version of this story is that a company I contracted with to do various big jobs around my home, sent a crew of Mexicans to do my roof. I went out to speak with the "jefe" and asked to see their papers. Three of them immediately dove into the truckbed of the nearest truck. Gosh it was great to put some fear into those little punks.
Bottom line? I sent them away, contracted with another company for "Americans only", and had to pay $1000 more to have my roof done, but happily did so, knowing that no illegals were working on MY home and that I wouldn't have to speak Spanish to ask them a question!! Sometimes, principals can cost ya, but we all have to do it. If my neighbors refused to have their lawns mowed by people who can't speak English.......if we ALL refused to have them do any work for us, they wouldn't find it so easy to meld in and stay.