A proper Caffe Americano is made with a shot of espresso poured into about 8 oz. of hot water. If the water is poured over the espresso, it will break up the crema.
Some coffeehouses hold the attitude that watered down espresso is no different from drip coffee. So when you order Caffe Americano in such places, they might just give you your typical, every day cup o' joe.
Beware, some establishments hold that Caffe Americano is made by passing a whole mug full of water through the grounds! This is NOT Caffe Americano, it's Espresso Lungo taken way too far, coffee over extracted to the extreme, very bitter.