I think their loss would be felt immediately. Meat in stores would become rare and incredibly expensive (guess who works the meat-packing plants) as would produce. Many/most restaurants would close down. People would instantly take note of disruptions to their food supply - just like during COVID.

The elderly and people with elderly family members who rely on (relatively) cheap home care from undocumented workers would notice the problems right away, too.

Stuff like overgrown lawns, no new roofs going up and a massive slowdown in new house construction would take a bit longer to be apparent.