Oh no, it's worse than that... we use the metric system to measure the customary system...

The Mendenhall Order marked a decision to change the fundamental standards of length and mass of the United States from the customary standards based on those of England to metric standards. It was issued on April 5, 1893, by Thomas Corwin Mendenhall.
[...]
Mendenhall ordered that the standards used for the most accurate length and mass comparison change from certain yard and pound objects to certain meter and kilogram objects, but did not require anyone outside of the Office of Weights and Measures to change from the customary units to the metric system.

https://en.wikipedia.org/wiki/Mendenhall_Order

Technically every unit in the US customary measurement system is just a weird conversion factor of an equivalent metric unit. At this point 1 yard was defined as 3600/3937 meter, which means 1 inch = 2.54000508 cm. By 1959 everyone finally agreed that this was stupid and redefined it as 1 yard = 0.9144 m (1 inch = 2.54 cm).

All measurements in the US are based on standard reference objects provided by BIPM.