Can't you convert the measurement from customary to metric, or from metric to customary? Why does it matter what system the tool was designed for?
Obviously anything that can be measured in customary can also be measured in metric.
Obviously anything that can be measured in customary can also be measured in metric.
However, this means that really changing over to metric, meaning also using international standards for tools, screws, bolts, wires, etc., needs buying new tools and material. I'm not sure how many metric tools there are in a typical US workshop, but I can imagine that they are not too common at the moment.
Buying two things to do one job - as is tradition.
But if you're e.g. repairing existing equipment, then the customary and SI units are incompatible. Say, a 1/4 inch bolt head is too large for a 6 mm wrench, but too small for a 8 mm (which is typically the next step up from 6mm).
For this reason I had to buy some wrenches in customary units to fix a lawnmower engine.
Where is the problem? Buy a 6.35mm wrench for your 6.35mm bolt head.
Oh, and the speedometer and the odometer. The digital ones are probably counting meters and converting though.
Anyway, the US already has the metric system for things that matter; science and most manufacturing. For things with wide reach, like distance signs, and speed limits, and quantities at the grocery store, those tend to be in customary units, because the switching cost is too high for the benefit.
Plenty of things end up as imperial elsewhere in the world, though. My lathe and milling machine dials are graduated in thous (thousandths of an inch). I've seen those on YouTube channels in other countries.