By my favorite source of information by committee, http://en.wikipedia.org/wiki/Metrication, the US shares its regard for the metric system with a few of its favorite countries, ie Liberia and Burma.

Judging from one Mars lander accident, even our best and brightest have a bit of trouble with the conversion, and while Huntsville TSA might have a former rocket scientist or offspring on its staff, the rest of TSA has a pretty good excuse.