Yeah, I do think we are under reported since the current mortality rate is 5.6% in the US. That seems too high from other data around the world.
S. Korea in my opinion offers the best estimate since they shut everything down and went for a large amount of testing right away.
Less than 2% of their tests have returned positive (20% for us) . There is a fair amount of confidence that they did better job identifying cases than anywhere else and enough time has passed where the number of new cases and the number of new deaths have been very low (close to zero), so the numbers are not likely to change much.
Their current mortality rate is 2.24%.
I haven't seen much data suggesting that it would drop much below 2%. There will be some variance based on age and health of the overall population, but I don't think the US is particularly young or healthy compared to the rest of the world.
Since the virus seems easily transmissible and no one had been exposed to the virus before this year, it would seem the maximum risk would be the entire population of the United States contracting the virus. If 2% die, our losses are 6.5 million people. Maybe that takes six months, maybe it takes two years, maybe we have a vaccine and we never get to 100%. In addition, it is possible we do not sustain a 2% death rate as we find out the true rate of infection and/or we are able to find treatments that aid in recovery.
There are a lot of unknowns. But 6.5 million deaths is the high end.