Yes . . .and Yes. Yes, I realize that a lot of hot, sweaty, often-demeaning work is being done by low-paid immigrant labor, both legal and illegal. And Yes, I DO think part of the change from the past (when Americans did such work) and today is that the current crop of younger Americans (from "Boomers" on down) has diminished work ethic and an unrealistic expectations (in my opinion) of work and wages compared with their predecessors. Having said that, I want to clarify my outlook on the situation and describe possible remedies.
The effect of having this supply of immigrant labor that is willing to work for low pay is to supress wages. If those workers weren't available, either the work would not get done or it would be necessary to raise wages so that Americans would be willing to do it. But, as we have this cheap labor to exploit, the wages are lower than they would otherwise be, and Americans mostly conclude that "I'm not beating my brains out for that chump change!"
This effect of suppressing wages doesn't just affect the low-wage jobs. Increasingly, work that used to be highly-paid (e.g., factory work, including antumaking) is disappearing too. Out-sourcing (the flip side of the coin from illegal immigration) sends jobs that Americans used to do out of the country, to lower paid foreign workers. Americans are being squeezed between cheap labor entering the US and jobs sent overseas to cheap labor countries. In India, medical test reports from the Us are being electronically-transmitted to be read by Indian doctors who make a fraction of the money an American doctor would be paid. Software programmers in places like India do the work for a fraction of their American counterparts. Increasingly, book-keeping and tax preparation services are being transferred from the US to other countries where the fees are less.
Are we Americans at fault for expecting to get paid the pre-vailing wages in our country? I don't think so. The cost of living here is an AMERICAN cost of living, so I don't think we should expect Americans to try to live herwe on the wages of a Third World country.
Take away the cheap-labor option and wages would re-set to what should be prevailing Americans wages. If the work is important enough to customers (say, home construction), they will pay the higher price. If the higher price squelches purchases of the item or service (e.g., less lettuce purchased), it probably wasn't that important (at least to consumers). Just as there was pain in converting jobs from high-priced Americans to lower-priced immigrants, there would also be pain in making the return trip. But, the value for America is that we would have our own people employed in these jobs again. And we would avoid the problems increasingly being presented by having influx of immigrants (especially illegals) into our country.
The other part of the solution is fostering in Americans a renewed work ethic and more realistic job expectations. Today, too many young people expect to go from high school to college and then to mid-management jobs pulling down $50,000 or more. What took their parents and grandparents many years to achieve, young people expect to receive when starting out. Also, they are encouraged to seek white collar jobs that allow them not to really do any work. This is why we don't have many young Americans willing to start as a construction laborer with the eventual plan of learning all the tasks and trades involved so that, one day, they can become site foremen or contractors.
Or, take the restaurant business: Few young Americans seem willing to start out working in kitchens or busing tables, so that they can gradually become cooks or chefs . . or know from experience how to manage the restaurant. Instead, they want to take management classes in college and, upon graduation, get picked up by a restaurant chain to step right into management . . without ever having done the various jobs in that setting. People that are very successful in their fields often had ground-level experience and worked their way up. There isn't any reason why young people today shouldn't learn and progress that way. We, as Americans, just have to teach this to young people as they grow up . . to foster more realistic expectations among the up-and-coming generations of workers.
Maybe that seems like a tall order, but if we were at that point in the past, I don't see any insurmountable reasons why we couldn't return to it. We . . the whole country . . . would be better off for it in the long run. More to the point --- if we don't do it, the future for our country looks mighty bleak to me.