Hi Benita,

If you have local language customizations they will over-ride the main language pack. I'm fairly sure Enroll is correct in all strings in the main en_us language pack.

Site Administration -> Language -> Language Packs, make sure the English US language pack is installed on the system

Site Administration -> Language -> Language Settings set "Default language" to en_us

For every user who would prefer US English you may also need to set the Preferred Language field in their profile as it may be set to the default British English (en)