Right now a person who is satisfied with a life of watching TV, eating processed food and maybe going to a movie once a week can live an acceptable life on welfare. If they had to work to eat, they would. There's your unskilled labor.

Another piece of the puzzle is the great amount of money that exists in the economy that is not liquid. It is tied up by the ultra-rich. They're not using it for anything. Once you are making $250K/year living expenses mean nothing. There's no reason the dollars can't be in circulation within the lower classes. The constant squeeze on the lower classes over the last several decades has only harmed the total economy.

I don't have an answer for how to get the illiquid portion of the economy moving again, but doing so would make the skilled labor market what it once was without immigration. There's your skilled labor.

You really have to realize that Americans are the best in the world. Yes, I am aware Jews lie and Asians are academic machines, but when it comes to the real world Americans are tops. The two biggest reasons are genetics. You just can't beat that Homo sapiens x Homo neanderthalenisis cross. And Americans are the best fed people in the world. You can't grow brains like ours without an abundance of food like ours. There is no substitute.

Importing labor is a costly mistake.