I was wondering the same thing. Price is supposed to be set at the equilibrium between supply and demand. Fewer immigrant workers should mean less supply of workers overall. If demand for workers stays the same, the price, or wage in this case, should go up. That must mean then that demand has gone down as well. Maybe businesses in construction and hospitality are hiring fewer people overall, for related or unrelated reasons.

There is another possibility: maybe the assumption that fewer immigrant workers would mean fewer workers overall was wrong. Maybe domestic workers are applying for jobs that would have otherwise been taken by immigrant workers, without asking for higher pay. There are plenty of American citizens who need a job, even if it is a relatively low paying one. Or, maybe increased immigration enforcement doesn’t necessarily mean a significant reduction in the availability of immigrant laborers. Maybe it’s a combination of factors.