There is some jobs however that Americans flat-out will not do.
Back before the days of the ACA I knew somebody who was running a dairy, they tried to get US citizens to work and milk their cows, they were paying over $3 an hour above minimum wage plus full healthcare benefits (ie: the employer paid for 100% of the employee's very good HMO plan) and they couldn't get people who would show up consistently, on time and not under the influence of something (at least not to the point where would it affect their work).
This was working inside shuffling cows through the milking parlor, attaching the milking machines, feeding the cows with the tractor/feed cart and scraping the alleyways with a skidsteer.
Aaron Z