It's only for calling American numbers while in Canada as per the add-on description:

“  Get unlimited long distance minutes for your calls from within Canada to the U.S.  Restrictions: Calls made to phone numbers starting with the following six digit combinations are not included in this add-on: 559-726, 712-775, 712-432, 605-562, 605-475, and 530-881. Calls made to these numbers will be billed at your standard pay-per-use rate.  “

If you are in the US, you are roaming and will need easy roam if you wish to make unlimited calls while in the US for a flat fee. Otherwise it's a really high pay per use rate.