Undocumented immigrants tend to be an overall good for the citizen economy since we can exploit them, charge them sales tax etc, and then not offer them public services in return. Hopefully the cheap construction labor will improve the housing situation in the US.
Undocumented immigrants have the same access to public services such as public education, medical care at hospitals, access to court systems, police, fire, etc.
Undocumented immigrants have access to the court system and police that will arrest them the moment they are found to be undocumented? Even if they ostensibly could use it they would avoid taking the risk
This point is about 20 years out of date and is no longer true in most of the country. Most local police, aside from border states, will not inquire about immigration status when dealing with the general population and many larger cities actually refuse to cooperate with ICE immigration detainers on inmates in their local jails for non-violent offenders.
And yet ICE hangs around those locations and even goes as far as to deport people they had a court order to not deport. That chilling effect would make undocumented immigrants avoid authorities unless you believe they are irrational.
I hate to be that guy but do you have a source on undocumented immigrants availing themselves of the legal system en masse in the US?