Even if you had the right to work in the US, it's by no means easier to get your first commercial job. The route is just as over here to become a flight instructor, and in the States there is a lot more competition for that job as well. Since you're not trained in the US you would find it very hard to find a job even if you had the right visa.
There is a huge shortage (instructors) in South Africa and I would recommend you to go that route. You would have to do instructing but you could move to other work pretty fast once you've passed the 500 hour mark.
Bottomline however there is no way around instructing.........