This country has, throughout its entire history, relied heavily on immigrants to make up the shortfalls in its labor force. A full stoppage of immigration is going to collapse the United States economy. Sooner than later.

Yes, if we remove our migrant population then we literally lose the majority of our food production workers. I think it'll also impact our construction work force, much of our factory workforce, our waitstaff, and various other jobs US citizens turn their noses up at - because those jobs literally would not sustain them and would destroy their bodies over time. Most of these jobs are sustained entirely by the desperation of immigrants trying to escape their prior circumstances.

Edit- added more detail in bold to make it clearer the the issue lies in how these jobs are conducted rather than being with US citizens.

Whoa whoa whoa, teenager is already a bit old and commands more hourly

Farms have historically used their children as free labor back when they were mostly family owned. That's why most schools here have a three month summer break. Now they want the factory farms to have that same perk, just with other people's children.