And the answer to this problem is: America must open its borders!
Same with europe. For the growth dependent economies to not collapse, they need to have a constant growth in POPULATION. When people stop having babies (whether they want them or not) thanks to all the forms of birth control available, the economy is in trouble a generation later. This was inevitable.
Eliminating abortion on demand would help.
We have 95 million people between 16-65 out of the workforce. Automation is increasing productivity and eliminating jobs, especially low skilled ones.
Immigrants grow old as well. We could increase legal immigration to 3 million a year from the current 1.1 million and it would have a negligible effect on our aging population.