Where did american measurements come from?

England....they predate the metric system, for example a "foot" is roughly the length of an adult male's foot.

Not sure why we don't use the metric system. There was a big push to switch when I was in elementary school, but it never happened.

English units measurements have been around longer than the math for decimal-based ones.

It was once easier to work with numbers that can be divided evenly by large numbers of smaller numbers like 12 (1,2,3,4,6,) or 360 (Degrees in a circle, well that's the same with SI, but it makes my point). The standards we based on something that everyone agreed to set by the ruling class (a king, or priest).

Decimal-based measurements didn't really take off until the slide rule and then digital calculators.

As far as change... that's a more difficult answer.

Great Britain. It is why we use practically all same measurements and units of measurements.

the greeks