Apple Watch SE

inayet176 wrote:

Does the Apple Watch with cellular purchased in the US work with a carrier in another country eg South Africa or does it only work on US carriers

No. Cellular models of the Apple Watch sold in North America only work on supported carriers in North America.

Don't try it. You will almost assuredly have problems. Make sure that you have an eligible cellular service plan with a supported carrier. Your iPhone and Apple Watch must use the same carrier,* and you must be within your carrier's network when you set up cellular on your watch. For more info, see:

Set up cellular on Apple Watch - Apple Support

A cellular watch bought in the US will only function in North America,Canada,Mexico and Puerto Rico anywhere else it will function as a GPS only watch.