There are no jobs that Americans are "refusing" to do. In every line of work everywhere there are Americans and legal resident aliens competing with illegal aliens. Many occupations have in fact reached the critical tipping point IN CERTAIN REGIONS where the wages and working conditions sink so low because the illegals will accept anything that's offered employers will find less and less legal workers willing to show up for that job.
There are still large parts of the country where illegals have not been able to penetrate the market/culture and degrade the going price for labor. There you will find child care workers, landscapers, janitors, truck drivers, constructions workers, warehouse workers and even agricultural labor performed by Americans and other legal workers at fair market wages in compliance with labor and tax law.
It's a complex issue because we allowed so many illegals here for so long. Now it's unfair and absurd to even consider deporting them by the tens of millions. What we need to avoid is falling into the carefully constructed cliche phrases designed by political operatives to constrain thought on the subject to a narrow focus. We won't solve these kinds of problems with the 30 second sound bite mentality.
That whole concept of "Jobs Americans Wont Do" is precisely one of those phrases. It's beneath you Newly to fall into that trap and fail to see the larger impact and complete set of variables and how they affect our society and economy.