Alas, very few Americans know as much as you do about the customary units of measurement.
For example, none of my students this year (I teach engineering) could tell me how many cubic inches are in a U.S. gallon (or an Imperial gallon); none knew that ounce can be a unit of volume, a unit of weight, or a unit of mass; none knew the difference between statute miles and nautical miles.
And what about imprecise measurements like a pinch, a dollop, and (my mother's best friend's favorite) a glug?
Simply use the metric pinch, dollop, and glug.
Yes, but we're illiterate in two systems.
SD