Some jobs can be easily exported, and others can't. A lot of the jobs being taken by illegal immigrants, such as in agriculture, construction, and hospitality, are not jobs you can really export.
Additionally, you can discourage companies from exporting jobs by increasing tariffs.
Not that easy. For example, if you are violating trade treaty obligations. You could easily end up facing international trade sanctions. Even if permitted, affected countries might be tempted to retaliate by raising their tariffs. Under some scenarios, you could set off a trade war that the U.S. might lose.
I'm sure that increasing immigration increases jobs, but that may be due to there being more people.
Maybe, maybe not.
The real question….
Thwere are a lot of real questions...
is if immigration increases the number of jobs available per a person in a population
and if it increases well-paying jobs with cost of living increases from more people factor in.
A second question, which begs another question:
What would cutting off immigration do to local costs?
You used the example of agriculture. If California were to magically export all illegal immigrants tomorrow by beaming them out of the country using a newly invented teleportation system at least two things would happen:
- Crops would rot in the fields because of the lack of sufficient number of workers to weed and harvest.
- The agricultural industry would be forced to pay higher wages to minimize the loss of crops. Although farm worker wages are far from the only costs of planting, growing, harvesting and delivering crops to the market, an increase in food costs to consumers could easily be the result. So consumers could lose out. Cost of Living Adjustments (COLAs) might not keep up. Further, as wages rise in the agricultural industry, competitive pressures against other industries would build in order for those industries to retain their work forces. This in turn would put upward cost pressures for other industry products.
- Upward cost pressures of agricultural products from California could easily ripple out beyond the borders of California because California exports food to the rest of the country.
A fourth question: What is fair for undocumented workers?
Anybody who thinks the current system is fair to that population probably also thinks that the earth is flat, that greenhouse gases cause the earth to cool, and that smoking is not harmful to health. Essentially, the lack of fairness to that group is the reason agricultural unions like the UFW are in favor of immigration reform. Right now, workers may be reluctant to join unions because of fears that come from being undocumented.