Wealthy countries almost universally depend on immigrants in the low end of the job market. On the average, the people able and willing to migrate to another country are cheaper, better motivated, and more talented than the low end of the domestic labor pool. Without immigrants, the society would not work nearly as well and many things would be more expensive. While the US has not created sufficient legal pathways for immigration, everyone is willing to turn a blind eye to illegal immigration, as long as it doesn't get too disruptive.

Skilled and educated immigrants, on the other hand, are not essential. Their presence may be beneficial to the economy, but things won't fall apart without them. At worst, the economy will be a bit less competitive.