the reasons might be the same, but the problems are different.
with mass illegal immigration, you are getting mostly very low quality people, which burdens the welfare system and causes crime to spike. the only jobs these people are replacing en mass our jobs that are done under the table anyway.
with a (supposedly) curated import of foreign workers like the H-1B system, you generally get higher quality people, lower rates of crime, and no burden on the welfare system, but jobs and opportunities for native above-table workers are replaced. Since our current system is also pretty bad at gauging the skill of imported workers, you also get lower quality work from them.
the reasons might be the same, but the problems are different.
with mass illegal immigration, you are getting mostly very low quality people, which burdens the welfare system and causes crime to spike. the only jobs these people are replacing en mass our jobs that are done under the table anyway.
with a (supposedly) curated import of foreign workers like the H-1B system, you generally get higher quality people, lower rates of crime, and no burden on the welfare system, but jobs and opportunities for native above-table workers are replaced. Since our current system is also pretty bad at gauging the skill of imported workers, you also get lower quality work from them.