Imagine if it’s not a job. Imagine if it’s a welfare. So government says, anyone that stand idly in Madison square will be paid $5 per hour. There is no productivity. Government is just insane giving money away. Will immigrants coming reduce that welfare pie? Yes.
Many jobs are essentially welfare. The salary does not justify the productivity.
I think immigration will reduce job but mainly only if the job itself is essentially implicit welfare.
Many jobs are not real job with normal salary. Minimum wage, for example, inflate salary for some job. Some jobs are created by stimulus. So those jobs are limited. More people taking that job means there goes the job.