Used to work at a car wash that was basically all Mexican employees. The job was fast paced and it got very hot/cold through the year where I lived and we worked 80 hour weeks. I got the job there fine but most Americans didn't want to work there or didn't last long because it was long hours and fairly physically demanding. Anyone could have worked there but my Mexican coworkers were absolute machines with how fast and thorough they were and they never bitched and complained or slowed down. I've never lost a job to an immigrant of any sort that I'm aware of because most of them are doing hard jobs that a lot of people born in America aren't willing to do. That car wash was super busy in the city I was in because of how fast and thorough it was and I hazard a guess that it wouldn't have done as well with without people willing to non stop keep moving for 10 hours a day 7 days a week.