I don't agree that this is the biggest crisis in American history, but by the time it's all said and done (including a second wave), it's not hard to see more Americans dying from COVID-19 than in the wars you mentioned. Especially if the country re-opens prematurely, which seems likely.
Moreover, I'm surprised you only mentioned wars. I think a better example would've been African-American slavery, even if it wasn't a single "moment", but I guess it depends on how you interpret the question.