I saw that too, and many of them claimed they learn both Metric and Imperial British systems and convert between them all the time. So this stood out now:
For the most part, we generally only use pounds, feet, miles. Everything else is a mystery. Even ounces, cups and gallons are some fucking magical mystery. Just follow the recipe.
This really isn’t an American thing - it’s just human, we can’t really visualize dimensions accurately unless we have a good reference. Some may measure the Olympic swimming pool in feet others in meters, but the effect is the same.