Welcome to the dimension of bizarro world that is so far away from reality it creates it’s own gravity and inverts itself.   This position is actually being broadcast on national television.  Simon Rosenberg appeared on Tucker Carlson’s TV show to defend illegal immigration.  In his position he attempts an economic defense that he has carefully written out for recitation.

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Rosenberg claims that because illegal aliens represent 5% of the population, and because the U.S. GDP is around $20 trillion – the economic value of illegal aliens is $1 trillion.
Let that sink in.  Simon Rosenberg is saying the U.S. Gross Domestic Product is an outcome of, or connected to, the size of the U.S. population.
For clarity.  There is absolutely NO relationship between the size of a nation’s population, any nation, and their Gross Domestic Product (GDP).  The GDP is simply the combined value of all goods and services produced in a country, minus their imported goods.  It has no relationship to how many people function within the country.

Robots and automation can drive GDP by producing products.  Phones and computing, as tools to drive productivity, can drive GDP.  Technological advancement and innovation can drive GDP.  The number of people within a country has nothing to do with GDP.
If population drove GDP then China (1.4 billion people), and India (1.3 billion people) would be #1 and #2 in GDP. They’re not. [*Note* The U.S. population is roughly 324 million.]  Indonesia would be #4 with 264 million people.  Conversely the U.K would be 21st with only 66 million people.

Rosenberg’s argument is the most absurd economic argument I have ever seen.  Within the manufacture of goods and services not all people are equally participating in GDP; nor are people factually a part of the GDP determinations.
How many pancakes you’ve ever eaten has no relationship to the car you drive.
If democrats are actually going to try this approach as a talking point for their DACA amnesty narrative I sure hope media pundits do a better job deconstructing the stupidity of the claim.
15 million illegal aliens (5% of population) are not driving $1 trillion in GDP (positive quantifiable economic activity).
How to refute this silliness?  Well, we can grow our GDP by reducing the amount of imported goods (true).  In doing so, if we put Chinese workers out of work we can grow our GDP (again true).  You’ll note that in each true statement the population of the U.S. doesn’t factually need to take action.
GDP is not related to population.  GDP is an outcome of the total value of goods and services produced, minus imported goods.  That’s it.