Free Condiments
Americans love their ketchup. So much so that it's pretty much always free either right on tables or at a communal condiment station. In other countries, these little extras are rarely just up for grabs and come with an extra price.
Singing in Public
Americans do like to sing in public, but why? Walking down the street singing and dancing is a pretty weird sight. In most other countries, if you have a place to be, you walk and you get there and you don't do any dillydallying in between.