Some jobs are new. In my area almost everyone has a lawn service. They can do so much better job than the amateur home owner, and at $30 a week its worth it not to blow a Saturday or Sunday having to do yard work. Same for having the car hand washed. Americans didn't ever do those jobs on the scale immigrants do.
You don't see as many cars driving around with body damage as thirty years ago because immigrant body men are available to do the work that few citizens did before. Roofs that previously would have been patched are now replaced.
Custom cabinets now are common whereas only the very wealthy had them thirty years ago.
Restaurants have a large staff of professional waiters instead of a couple gum chewing Floes. New homes are built in a fraction of the time they previously were.
Remodeled kitchens, new floors, sprinkler systems, and swimming pool additions are more common today than thirty years ago.
Machine shops and small manufactures are producing products that simply weren't being produced thirty years ago. (If they come we will build it)
These aren't jobs previously done by citizens, these are jobs that simply weren't done before we had the skilled plentiful labor to do them. Take the immigrants away and there are no citizens to replace therm at any wage. The lawns just won't get manicured, kitchens remodeled, car dings repaired, and water glasses kept full.
And the majority of the work is being done by unlicensed, uninsured, underqualified people.