[at]Kallas, SAA flies into Terminal 4 at JFK. usually arrives around 6:40am- but including taxi-ing to the gate you will only get off the plane after 7am. it usually takes about an hour to clear customs at JFK- give or take if you arrive with another flight (shortest we've had was 40min but once it took over an hour and a half). For first time entry with immigration that might actually be shorter, as you won't line up with the rest from passport control- you will most likely go through the ESTA etc line? (this was recently changed) and again it will depend on any other flights arriving at the same time. This again can differ- our son in law had to go to a second counter/ office as the first officer wasn't able to click on a button (jip) to activate his GC and he had to line up at another office, where he waited for more than an hour- just to have a supervisor click the icon.
you will have to pick up all your luggage and clear through customs before you can take your connection flight. You can make use of the Sky Train on the 3rd floor to connect to all the other terminals. Its less than 15 min ride.
There's a Delta connection flight desk right outside the entry into the arrivals hall (to your left). I am not 100% sure if this is for all airline use or only Delta? I've hear of people using it for other airlines too
Just a note: On Saturday I arrived back from SA from a short trip- and ALL the passengers from the SA 203 flight was pulled over for luggage checks from customs. There was a whole lot of customs police and everyone's bags were searched and some where even x-rayed. Wrappings were cut off etc.
If its a normal day with normal circumstances you should be ok with 3 hours, but its no guarantee
Good luck, All exciting. Its also great if the company is willing to fly you in for an in-person interview- this is usually a great sign as US companies will have 2-4 telephone interviews before they invite a candidate for face to face / in person interview