Well.
It is true you may have hard luck finding a paid for-flying job in USA with fresh CPL. Having SOUTH african CPL or USA does not make any difference to your career path. However, South African CPL may land you a job in Africa since majority of African companies are South African registered. BUT then again, you must still have compound luck to get a job on SA registered aircraft with little experience-that is to say SA CPL, if you are not south african citizen.
There are a lot of south african pilots without job, and you find them through out Africa. Once they have enough experience, some join their regional airlines.
IF you come from a country where aviation is large and active, say Nigeria, Kenya or Ghana, well, you can choose any country to train from. Both USA and South Africa are competitive in cost of flying training-USA being slightly cheaper depending on the school.
BUT, if you require visa to goto USA for flight training, it can be a bit tedious experience to get the visa, and can be lengthy procedure. That said, South Africa remain your best option....south african student visa is straight forward, that is if you also require south african visa.
About 'many flying hours' on multi engine-well that my friend will depend on your pocket. it is possible, but it can easily tripple the cost of your flight cost. And what multi engine are you talking about? Beech 1900, or Boeing? then that could be worth while---that is if you can foot the expense, say 5000USD and hour---and since you want many hours, say you are talking of 50 hours on it and above? Normally 100-500 hours on type, to be considered for employment on type..... well you do the maths.
OK sarcasm aside,a multi engine rating will help you have multi engine cpl licence. But many multi engine hours on a piston aircraft may not help you much in the job market once you complete. Very few(none) company will employ you fresh from school with 300 hours and give you their shining piston seneca to fly solo and take tourist to their dreams....because you have many multi engine hours.
So in general: You can goto USA, or south africa. No big deal. If your plan is to fly in your country, you will have to convert the licence anyway.
Hmmm...once you a pilot, some day when fly in Africa.... you may have a chance to share airspace with some of your russians friends who claim they do not log african hours. You will then judge the super pilot in them.....