There is no evidence for an objective concern though. Ghana is not in a better position to know anything about the safety of this airframe than the FAA or Delta themselves, and Ghana has a long history of politically-motivated actions in aviation.
Before you start talking about ETOPS approval, maintenance practices and crashes, it would make sense to have some shred of evidence for a safety concern on this particular airframe rather than just a couple of air returns due to minor issues — the kinds of returns that happen daily all over the world, to new and old frames. Two air returns in a week on the same frame is rare but not unheard-of, and it's notable that one of the air returns was following maintenance action in Ghana that apparently didn't solve the issue.
Before you start talking about ETOPS approval, maintenance practices and crashes, it would make sense to have some shred of evidence for a safety concern on this particular airframe rather than just a couple of air returns due to minor issues — the kinds of returns that happen daily all over the world, to new and old frames. Two air returns in a week on the same frame is rare but not unheard-of, and it's notable that one of the air returns was following maintenance action in Ghana that apparently didn't solve the issue.