The US is the only country in the world that does not use the metric system
The metric system was first introduced in the 1790s in France as a way to homogenize measurements. During the mid-20th century, it was adapted into the International System of Units, which was adopted by many leading powers.
Today, most of the world uses these standard measurements in everything from trade to education. All but one nation have adopted it as their official measuring system. The US is the only place on the globe that uses a different one.