What does "U.S." mean in English for Spanish?

In English for Spanish, "U.S." means:

EE.UU.

Listen to "U.S.": (If you have an HTML5 enabled browser, you can listen to the native audio below)

This is a word that is used in the GamesForLanguage English for Spanish Language Game in the following scenes:

• English for Spanish 3, Level 1, Scene 3