"Every year way more patients are poisoned by their doctor under the inperial measurements system because it's too complicated."
Could you cite some examples of this Imperial confusion of which you speak? My memory is not perfect but I can not remember ever hearing of an event involving a miscalculation in a dose or application in the medical profession. I have no doubt it has happened, just not with the regularity that you imply. And if this were happening, I would think the numbers would go down; because the previous years events would highlight the need to pay attention when dispensing medications; not up which would imply a total disregard for the health and safety of patients.
The US diverged from the British Imperial System in early 1800s and has been using the USC (United Sates Customary) system since that time.
Yes, many here still refer to our system as Imperial, myself included at times. But it is not 100% the same as the British Imperial System of measurement from the early 1800s.
https://en.wikipedia.org/wiki/United_States_customary_units
My doctors all use metric system. My height and weight are recorded in cm and kg, and all the meds I have ever received have been dispensed in mg or ml.