The reason immigration policy isn't enforced 100% is because that's a guaranteed way to tank the economy... most farm laborers in california and the deep south are undocumented, companies like this so they can get away with abusing their workers and threatening them with deportation should they try to report labor violations... if there were no undocumented immigrants, companies would have to hire citizens or legal residents. Now, in the abstract, this is a good thing. I would support this, except... when they hire these people, they then actually have to follow safety regulations, minimum wages laws, etc. In response they would probably just raise the price of food rather than hurt their own pocketbooks, which would vastly increase the cost of living for all americans, vastly lowering our disposable income, sending the american economy into a death spiral.
I mean, there are totally ways around this, but they involve things like allowing the government to grow food and compete in the marketplace. You know, policies you'd probably disdain as "socialism".