I want to purchase one of the discounted games from the PSN store shown here but according to that you need a US PSN account and my current is an SA account.
So what are the implications of creating a US account and will it be possible to play the game using my SA account?
It will be possible to play both your US and SA digital games. Every account that is logged in on your console will have access to all the games installed on that console despite which account was used to download them. I used to have a SA PSN account but have since moved to a US based account due to the great deals that are always there and I can still play the games I downloaded using the SA account and the SA account can also play the US account's games. More like programs installed on a PC for all users, anyone who logs in can access them. Go for it, got myself FarCry4 and TLOU Remastered a couple of weeks ago