This question has certainly brought forth an exemplary outpouring of stupidity and confusion.
I think that Americans feel The Metric System may be too cerebral in picturing it. A mile is a mile. An inch is an inch.
But, A kilometer...A centimeter. How do you picture these? Concepts?
What you say here is that there is something inherently more difficult to "picture" about kilometers or centimeters than there is about miles or inches. Have you no idea what an idiotic statement that is? They are all equally arbitrary measures. What enables someone to "picture" a given measure is his FAMILIARITY with it, and nothing else. Someone who grows up estimating distances in centimeters and weights in kilos will find it just as difficult to make estimates in inches and pounds as you find it difficult to make estimates in his system.
I'm starting to get that concept now and it's really not all that hard to grasp once you realize metric is more precise than American Standard.
How is it more "precise" to measure something in the metric system than in the old English system? If someone says that this rock weighs about a kilogram and I say that it weighs 2 pounds and 4.0 ounces, then my measurement is more precise than his. It doesn't matter one fuck whether you use the one system or the other. What is precise or imprecise is not the system of measurement, but the use that is made of it.
Now if I measure distances in, say, paces, then
that is a system of measurement that is less precise than one in, say, meters -- or, for that matter, feet. This is because the pace, unlike the meter and the foot, is not a fixed measure.
SI units are great for the science geek crowd, as the base-10 hierarchy provides virtually limitless precision. It's great for calculations on paper, but a royal PITA for application to everyday real-world usage where people already know how far a mile looks, how big an acre plot looks, how heavy a 5 pound bag of sugar is, and how much room a gallon jug takes up in the fridge.
Congratulations, you have combined the idiocies of both of the first two posters: that the metric system is more precise than the English system, and that the metric system is somehow inherently -- and not merely in relation to the degree of a given practitioner's familiarity with it -- less applicable to estimates by eye and by feeling.
I find it really depressing that people can be so fucking stupid.