Kokevi:
The voltage and cycle differences aren't a train-smash and can usually be solved with a good transformer. In fact, many newer A/V products sold in the USA are 100-240 voltage.
The BIG issue is whether the TV can cope with "multisystem" video input (whether by HDMI or other input ports). Unfortunately, most North American TVs aren't ready for play anywhere other than NTSC-land. Similarly, most North American DVD players read nothing other than Zone 1 by default. Yes, most local equipment is "multisystem" and can operate in several places in the world. However, your question isn't about what's available locally. Rather, you want to know whether your American-purchased TV will work here in SA. When importing an American device, I've checked the Internet for "hacks" on the device's make and model number. Often, there is a means of "reprogramming" the device to work as "multisystem" - even if PAL doesn't appear in the default menu system. My son's portable DVD player had a successful "hack" (sequence of keys entered on the remote to reprogram it). My daughter's TV/DVD Player had no such luck.
If you ask most American sales representatives if the TV will work with PAL, they look at you as though you're from Mars. To be fair, many South African sales reps are equally uninformed. My recent Sony DVD Recorder purchase began with a local sales rep telling me that it was incapable of playing Zone 1 DVDs. I pulled one from my backpack, slipped it into the player and it loaded perfectly. He quickly left me with another sales rep and shifted to another customer.
As an earlier comment stated, you'll also need to know whether the TV can handle PAL I - so that the sound will function properly.
Your best bet is to search the Internet using the TV's make and model number + "PAL compatability." You might even throw in a reference to "hacks."
If you decide that you'd like to discuss the issue with a knowledgable sales rep in the USA, consider a company that sells world-wide-use electronics (like
http://www.western-international.com/).
Good luck!