The US is trying to convert to metric! Under Gerald Ford the Metric Conversion Act was signed into law which stated, "the preferred system of weights and measures for United States trade and commerce."

The problem is that it is a voluntary process and attempts like The Metric Marvels have never been very successful in persuading your "average American" to stop using it in their every day lives.

This is an ongoing process and as recently as last year a bill was proposed in Hawaii to make the metric system mandatory within the state.

http://en.wikipedia.org/wiki/Metrication_in_the_United_States#21st_century