You, in this country, are subjected to the British insularity in weights and measures; you use the foot, inch and yard. I am obliged to use that system, but must apologize to you for doing so, because it is so inconvenient, and I hope Americans will do everything in their power to introduce the French metrical system. ... I look upon our English system as a wickedly, brain-destroying system of bondage under which we suffer. The reason why we continue to use it, is the imaginary difficulty of making a change, and nothing else; but I do not think in America that any such difficulty should stand in the way of adopting so splendidly useful a reform.--Lord Kelvin (Sir William Thomson), in a lecture delivered before the Academy of Music, Philadelphia, under the auspices of the Franklin Institute, 29 September, 1884, printed in the Journal of the Franklin Institute, November 1884, 118: 321-341.
Drugs have taught an entire generation of Americans the metric system.--P.J. O'Rourke
Marge: Now, I know you haven't liked some of my past suggestions, like switching to the metric system --- The Simpsons episode "A Star is Burns"
Abe: The metric system is the tool of the devil! My car gets forty rods to the hogshead and that's the way I likes it.