If these jobs were offered at higher wages, there would be Americans willing to do them. However, when you have all these illegals willing to work for lower pay, why offer the jobs at pay rates attractive to Americans?
Exactly if we really had a shortage of unskilled, uneducated labor in this country, then jobs that were unskilled and did not require an education would be offering higher and higher wages to attact workers. Which obviously is not the case.