Sudan by trading (export: China $3.06B, the United Arab
Emirates $805M, Saudi Arabia $683M; import: China $2.58B, India $912M, Jordan $781M, Egypt $596M and Saudi Arabia $515M). Whereas South Sudan has established economic relations mainly with non-advanced countries (Pakistan, Ethiopia, Ukraine, Uganda, etc).
In fact, some Russian experts regard South Sudan as an American geopolitical project. The only opponent to the USA could be Beijing, which has been present on the South Sudan’s market long before.
https://atlas.media.mit.edu/en/profile/country/sdn/; https://ria.ru/economy/20160928/1478059973.html;