In the United States we tend to think of ourselves as forward-looking, on the edge. This is where technology advances; this is where the Internet was invented, where almost all the software on your computer comes from, where cell phones were developed, etc. This is where the biggest advances in medical science arise. Other countries might do amazing things too (we are particularly envious of the Japanese when it comes to manufacturing and engineering) but we have this idea that we invent stuff and then sometimes other countries take our innovations and find ways to mass-manufacture them and make them smaller, so we're still the innovators.
We imagine ourselves to be social pioneers, though we're not as sure about that as about technology. Aren't we the wave of the future when it comes to political outlooks, civil rights, egalitarian attitudes towards acceptance, views on the environment? Okay, the last eight years we've taken a drubbing in that area, sure, but generally, on the scope of the whole history of the country, we see ourselves that way.
We're certainly quick to make fun of older countries for being mired in their history. Those silly British, still driving on the left side of the road and refusing to adopt perfectly reasonable spelling reforms proposed two hundred years ago! Their legal professionals still wear wigs! They still think the first floor is not the ground floor! They still call tungsten "wolfram"!
And yet, Americans whine about the transition to the metric system, now into its fourth decade, and still refuse to adopt it. It's too hard! We're too used to what we've always used! We're too set in our ways! And yet nearly every other country in the world, even the British (who we love to make fun of for being mired in its history) did it ages ago. Our only fellows in the Metric Holdouts League are Liberia and Myanmar -- now that's a proud company! We've got no grounds for making fun of anyone about anything as long as we still have to count the ounces in a gallon.
Though we do owe the soft drinks industry one thing. Most Americans have no ready grasp of how long a kilometer is or what a kilogram weighs -- at best, they can do the conversions in their heads, which is not the same -- but everyone can imagine how much two liters is, without even a second thought.
(Yes, I know they still refer to ounces in the U.K., but they know their metric units without having to do conversions, and use them in everyday life, which is more than we can say.)