I'll go one further.Until American consumers understand the true cost of doing business,you won't curb the flow of illegals.
Let's say you want or need a retaining wall built.I come in(I own a landscaping company) and give you a bid.Mr.Illegal Hirer comes in a underbids me by 35%.Who are you going to hire to do the work?Be honest with yourselves.You're going to hire the lower priced bid almost 90% of the time,unless I was referred to you by someone you trust.Even then,you may go with the lower price.
Mr.Illegal Hirer doesn't pay unemployment insurance,half his employees SSI,a decent wage,or workmans comp.,so he can throw out a very attractive bid for the same work.