Italians don't drink tea

Well, that's not entirely true, but we know that espresso & cappuccino is the favorite wakeup beverage.  But anyone who has ever tried cooking an American recipe in Italy knows one thing: you better have your own set of standard teaspoons handy for that bit of salt that can make or break the dish.

guzzini posate - place setting

Of course, if you're a chef truly worth your salt, you can eyeball your teaspoons of this and that.  Recently, I held a mini brownie-making session with a roomful of Italian friends (actually unveiling my secret recipe given the difference in ingredients & ovens), but when we got to the teaspoon & tablespoon parts, things got seriously messy.  That's because the teaspoons that we Americans grew up with and that are rarely used to stir tea but are for wolfing down your Frosted Flakes, and the tablespoons you almost never use at the table are of a totally different standard than European sizes.  
The teaspoons are actually small enough to fit handily into a cup of espresso, but you can barely get three corn flakes to sit firmly on them for the time it takes you to raise your spoon from your bowl to your mouth.  
Try the tablespoon, and you realize it is only good as an assist for twirling pasta on the back of it, because going in frontwise is a wholly difficult proposition.  So, you learn to either bring what you're used to (from Italy to the USA or vice versa) so you can get it right, or, you learn to wing it on proportions when it comes to your muffin fix.
After you've got your dry ingredients down pat, you can then move up the scale to translating sticks of butter into grams and finding 'self-rising' flour, something that is new to pasta-making Italy, but now available almost everywhere (farina per torte).
These slight differences in national ingredients is what makes American-made gnocchi stick to the roof of your mouth, and makes your Italian-made corn bread (should you ever be so desperate as to try & use polenta) come out tasting like you've just eaten a bag of broken marbles.
And let's not even think about the UK Imperial-vs-American weights and measures.  I recall being thrown off by the very idea that a foot was the length of the king's actual foot (and I don't even want to think what the inch might have been based upon).  
I have however found this terrific conversion table by what's cooking america for any industrious chefs out there.