You can get 10% off on the US PlayStation Store by using the following voucher code:
The voucher expires the 30/03/2015. Excludes game pre-orders and PS+ subscriptions.
Please note: To access the US web store, you need to be logged into your US PSN account or signed out of your SA account.
Setting up a US PSN account on your PS3 or PS4 is a simple process (check here). You will then be able to buy games on the US account and play them on your SA account.