To your first point: The wall in Texas is expensive and poorly thought out - no argument there. A better wall could be built but possibly not in the current political climate

So you're basically saying that you want to put up a wall to prevent all of these people who are often fleeing for their lives just so that you don't have to deal with the monetary consequences. If that's fine with you, then I can't really argue with you, i guess.

Isn't that what EU is doing by making a deal with the Turkish dictator to keep the migrants out and not letting non Syrian economic migrants in. Unlimited flow of people into your country just is unreasonable and creates way too many problems and is a net drain on your economy and standard of living. There aren't enough jobs as it is for both skilled and unskilled laborers in this country so more people will just make the problem worse check out the labor participation rate (% of people employed) Its also costing Europe 15K per person per year so its a huge resource drain.

As for farming you are right. We may loose strawberry farming in California. Its unfortunate but they probably don't have the water for it anyway. Farmers will have to switch to less labor intensive crops, some farms will close.

I'm sure the Southern states before the end of slavery made the same argument that the author of the article made that if plantation owners had to pay the slaves they wouldn't be competitive. As a country though we have to enforce labor rights and standards as failure to do so will cause a huge decrease in quality of life for most people. For me American workers being too expensive is not a good justification for allowing farmers to smuggle people in and treat them like slaves with no legal protections. If the job cant be done when paying people a fair, and legal wage then the job shouldn't be done.

Per your last link farming for export in Hawaii probably isn't realistic, being that the price of land is insane and transpiration can fuel and labor costs are insane. It will be replaced either with a new housing development or lower cost/impact farming for local consumption. Similar things will happen in California. Either more automate crops will be sown or land will be used for other things. Plastic tasting strawberries that are available all year may become too expensive but they will still grow in many regions and be available for you to go and pick them ripe and delicious in season.