Why the Metric System Matters is the title of the latest TED-Ed lesson. The lesson explains how measurement systems evolved through history including the historical event that hastened the adoption of the metric system throughout most of the world. The lesson also explains why the United States doesn't use the metric system.
As is noted in the video above, many Americans are not comfortable with the metric system despite the fact that it's the universal standard in mathematics and science. The Buzzfeed video embedded below captures the trouble that Americans have with the metric system.