When building target audiences for Facebook Ads, usually we recommend separating USA into its own audience, and then choosing an interest to go with that country, e.g. Romance Novels
Then, another audience is World (Everywhere), excluding the following countries:
Afghanistan, Angola, Azerbaijan, Bosnia and Herzegovina, Bangladesh, Burkina Faso, Burundi, Benin, Brunei, Belarus, Democratic Republic of the Congo, Central African Republic, Republic of the Congo, Côte d’Ivoire, Cameroon, Curaçao, Djibouti, Algeria, Estonia, Egypt, Eritrea, Ethiopia, Gabon, French Guiana, Guernsey, The Gambia, Guinea, Equatorial Guinea, Guatemala, Guam, Guinea-Bissau, Guyana, Indonesia, Isle Of Man, Iraq, Jersey, Kenya, South Korea, Kuwait, Liberia, Libya, Morocco, Moldova, Montenegro, Madagascar, Myanmar, Mongolia, Mauritania, Mauritius, Malawi, Malaysia, Mozambique, Niger, Nigeria, Nepal, Papua New Guinea, Pakistan, Serbia, Rwanda, Saudi Arabia, Sierra Leone, Senegal, Somalia, South Sudan, Chad, Togo, Tunisia, Turkey, Taiwan, United States Minor Outlying Islands, United States, US Virgin Islands, Yemen, South Africa
Of course, this would also target an interest, e.g. Romance Novels.
Sometimes you find outside the USA converts best, sometimes they both convert highly, it pays to test.
Yes, sometimes countries like South Africa will convert. But right now the Rand is so low that it generally is not worth it to advertise there, and best to go with keeping it simple and using those above tips for country targeting.