I have an extensive education including an MS in Mathematics - including all the physics and chemistry that such entails. I've taken Modern (Quantum) Physics. All science, and all word problems in math, is taught in the metric system. Sadly, when I was in primary and secondary school I was taught in IPS/SAE/Imperial. I don't know if this is still done today.

Stateside, motor fuel is sold mostly in gallons. Fluids for drinking are sold in ounces for small amounts, in liters for larger sizes. In vehicles, wheelbases are inches, as is interior space. Engine displacement is generally in liters with cubic inches in parentheses. Speed is almost exclusively in miles per hour although meters also show KPH. Acceleration is always mile-based. Athletic events are all metric, except for the more popular team sports. These will be very hard to transition. Although US commerce has official been based on the metric system since 1790, precious metals are sold by the Troy ounce. and crop yields are in bushels (from acre-based farms). Depths are in feet or fathoms, and the nautical mile (and knots) prevails upon the waves. All thiis could be brought into the world standard SI within a generation, but after at least twelve, it has not been done.

I think in miles per gallon and cubic inches (for autos). Seat height is in inches. When I described my location, I had to convert miles and feet into kilometers and meters. Any (technical) calculation I make is in metric. When I submit a design to a manufacturer or a machine shop, I give it in metic values. They invariably "inch" back at me. So, if I inadvetently give you clearnces in thousandths of an inch, I'm sorry. Old habits die hard.