They document themselves.

If they don’t, well. Who cares ?

Most places won’t hire undocumented. That actually is illegal.

If they commit crimes they get arrested and deported.

If they aren’t committing crimes then why do I care if they are here or not?

They can’t get food stamps or unemployment. They don’t drain any resource.

Most undocumented people here in the U.S are here for family reasons. Or something work related. Not nefarious reasons.