What percentage of people within the US die while their life
insurance's in effect, and, thereby, are able to cash out on the
promised policy?

I would guess 1/2 of the people who die daily have no life insurance
other than the Social security death benefit which is about $300.
Another 15% are paid less than $2000 for a variety of reasons, such as
they barrowed money against the policy, A nursing home, IRS, or other
government agency seized their assets. Or they cashed the policy to
pay medical expences shortly before death.  Neil