Is there any hidden or declared crisis threatening the relations between US and South Sudan?! This question now is very serious than any time before. The matter will not reach very far expectations. South Sudan is still an American achievement, the newborn baby for Uncle Sam, but this baby needs sometimes to be educated! Uncle Sam will not deprive the baby from some gifts and biscuits but he will not allow him to play with fire or to touch electric wires. Obama himself took very strong actions against South Sudan government during Heglig War but for sure he is not going to take tougher stance on South Sudan or at least he is not doing that anytime soon. Why? Because he has very little to gain from disturbing  his allies, moreover SPLM Government is already in a mess!
Obama suffered a lot from South Sudan, according to some leaks: Kiir kept Obama waiting for over a half-hour for their first meeting on the sidelines of the U.N. General Assembly session, this information could not be false, it is true, read this piece from Alan Boswell's article; "Failed State Lobby":
(U.S. officials are quick to pay lip service to the problem of corruption, but there is so far no bite behind the muffled whimpers of protest. Unlike the tough, targeted U.S. actions against leaders in countries such as Kenya, Washington has not threatened travel bans or publicly frozen bank accounts of leading government officials, U.S. officials say. Despite providing military support -- to the tune of about $300 million in taxpayers' money -- since 2005, the United States does not seem to have a strategy in place to induce South Sudan's leaders to reform their ways.
That is true despite President Kiir's estrangement from Obama, which one source close to U.S. policymakers described as "probably irreparable." In September, Kiir kept Obama waiting for over a half-hour for their first meeting on the sidelines of the U.N. General Assembly session, according to several sources with knowledge of the meeting. Then, over later phone calls, Kiir personally denied to Obama that South Sudan was providing support for rebels across the border -- despite U.S. intelligence that clearly established otherwise. Relations turned even more sour in early April, when Kiir promised Obama that South Sudanese forces would not strike north and capture Heglig, a disputed Sudanese oil field, sources briefed on the conversation said. Several days later, South Sudanese forces -- working in coordination with the Sudanese rebels Kiir denied links to -- did just that, sparking international outcry.
But even if U.S. policy errors are partly to blame for the country's mishaps, don't expect the White House to take a tougher stance on South Sudan anytime soon. Why? Because Obama has little to gain from upsetting the SPLM's friends)