After https://www.populationpyramid.net/united-states-of-america/2020/

    The  age pyramid of US shows very clearly that the population over 60 years old is already decreasing after 60 years old. This category represents 22.7 % of the total population.
As the average age of death is statistically about 80 years (in the absence of preventive treatments of the diseases of aging).
We can conclude that 22.7 % of the current population of US will be statistically dead in the next 20 years and will have to be replaced in the absence of preventive treatments for diseases of aging.