On the iPad, please go to Settings > iTunes & App Stores > Apple ID: > View Apple ID > Country/Region, and change to your current country location.For the iMac, go to iTunes store in iTunes application, then scroll to the bottom right, then click on the country flag icon, then change to your current country location. Also, if needed, on iMac, click on your account at the top right in iTunes application, then click o nthe Change Country or Region, and continue.
More details as needed:
http://www.ilounge.com/index.php/articles/comments/switching-an-itunes-store-account-to-a-different-country/Please let me know if there is still any issue. Thank you