Keep in mind I originally did this exercise back in the early days of the pandemic with limited data. I can't locate all the original page I used but these new numbers work out. Going by previous estimations if everyone in the US got infected theoretical death is 1.9% of the population [1]. In march 37.7%[2] of hospital visits required the ICU and 13.6%[2] of hospitalizations resulted in deaths. So here we make the big assumption that everyone who died of COVID did so in the hospital which means 14.6% of COVID cases require the hospital. The next assumption is that if you don't have access to an ICU with COVID-19 you're going to die. We can increase "hospital" capacity with beds in stadiums and schools and such but we won't have enough equipment for more ICUs, so assumed ICU rate multiplied by assumed hospitialization rate is the worst case deathrate of everyone getting infected in the US at once in the early days of the pandemic, which is 37.7% * 14.6* = 5.4%

I'm not fooling myself with precision so I concluded roughly 5%.

An interesting note after the fact that the early estimated US deathrate of 1.9% tracks modern data pretty well [2] which is 1.8% (605,792/33,769,600).

[1] Sources and math, I used archive.org to get the numbers from March 2020 https://www.worldometers.info/coronavirus/coronavirus-age-se...) https://www.census.gov/data/tables/2019/demo/age-and-sex/201... age-sex-composition.html

  age    pop(M) deathrate theoretical-deaths
  00-39  169.5   0.2%     0.34
  40-49   39.9   0.4%     0.16
  50-59   41.5   1.3%     0.54
  60-69   37.9   3.6%     1.36
  70-79   23.4   8.0%     1.87
  80+     11.9  14.8%     1.76
  ----------------------------
  total  324.1            6.04
  6/324.1 = 1.9%

[2] https://gis.cdc.gov/grasp/COVIDNet/COVID19_5.html

[3] https://www.nytimes.com/interactive/2021/us/covid-cases-deat...