Can you name even a single country that adopted its customary
units from the US?

You raise an interesting point.

The two nearest neighbors of the US use the metric system.

Let us consider the Mexico/US border.

On one side you have the richest society in the world. On the other side
you have a metric system and third world living standards!

Or, (for you racists) take the US/Canader border: By the standards of the
US, Canada doesn't have a significant military establishment. Yet it
manages to have a lower relative national wealth. It has MUCH more OIL and
gas than the US, etc. etc.

SO: just WHAT IS THE PROBLEM with Canader and Mexico?

The Answer: The METRIC SYSTEM!