They clearly mean from one specific event. What one event in the USA has lead to 2 million deaths? You're combining all deaths and treating it as if it were the same thing.
Couldn't that be applied to deaths from other diseases? Why wouldn't all influenza deaths be considered one event by this standard?
There have been six of them in the last 140 years with respect to influenza. The Spanish Flu pandemic killed 675k (in the USA, like 50 mil worldwide or something wild like that.)