There are a bunch of stuff that make this hard to calculate. One is that cases are undercounted, while deaths are almost certainly not. Another is that deaths are correlated to available healthcare. 3x cases would mean that the standard of care goes down, which means more deaths. More deaths would probably also mean increased "protective" measures. Risk tolerance (and risk of infection) is elastic. Seeing 3x more deaths would certainly mean at least some people would take it more seriously, which reduces risky behavior and slows down cases, etc.

So you're right, if worst case everyone in the US gets infected, we're in for a lot more deaths, but aside from an apocalyptical R=100 type disease, not everyone is getting infected. The more infections there are, the more preventative measures are taken, etc.

It's a hard problem.

I'm pretty sure what we saw this year demonstrates that protective measures are far less elastic than we might assume.

This calculation does not take into account a collapse of the medical system. The problem with covid is the speed of its spread. We see this in India right now. There are not many cases per capita but their limited health care system could not handle this and people suffocate to death.

This is very wrong because as another comment mentioned, we are constantly on the verge of collapse of the health care capacity. I have friends who work in hospitals and the measures a government in Europe seems to take seems to always have as loose as possible measures while keeping the health care system at near maximum strain. Many people recover from covid in the hospital and even bigger problem is that if many more people are sick from covid, the people with other unrelated issues are lacking health care attention. One number I've heard is that we will see an increase in deaths from unrelated health problems which would usually get detected on time but since it's hard to get an appointment

Great answer, thank you