I understand where the 0.05% case rate number comes from (reported deaths divided by reported cases). I do personally think the reported deaths number is probably slightly over-reported and the reported cases is significantly underreported.
Even if the case fatality rate is accurate, I just don't think it's useful when assessing personal risk unless you routinely go out of your way to catch covid. If you start getting into that level of detail, you at least need to correct for comorbidities as well.
Specifically, when I say that it's an order of magnitude less likely for a teenager to die from covid than a car accident, I don't mean a teenager that caught covid or a teenager that was in a car accident. I mean a randomly sampled teenager out of the 60 million or so in the US.
The truth is we don't know how many kids in the US have had COVID, but I'm pretty sure it's not 100% of them -- which is why the number I cite is the estimated case fatality rate and not just the total number of cases.