How do I prevent the Select Language prompt from displaying when the locale is not "English (United States)"?
There is a radio button in the Build Options page that allows you to turn on or off the "Always prompt for installation languages".
If the option is deselected on a computer where it is not able to detect the language of the computer as being one in the installation, it will continue to prompt for the which language the installation should run in.
The only way to suppress the Select Language prompt for an English computer is to ensure that you include all the English language codes in your installation. Example: ENA, ENU, ENG.