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Comic strip of a ghost and a person with the American flag pasted on the head. The ghost repeats "Boo!" in the first three panels without getting any reaction, but when it in the fourth panel says "kg, cm, km, °C" the American gets scared and screams "AHHHH!!!".
Edit: fixed alt text
Well, there is basically only one country that has been too afraid to change from its archaic measurement system to the internationally agreed upon standard.
3 actually, and it's not a good group.. And I'd like to say that most Americans actually support the idea of switching, but as a stubborn guy who uses metric for everything here I can sadly say that they are not by a long shot.