Reading the intent behind that statement, though, that Nigerians have succeeded in America despite any hinderances they may have faced due to wider societies treatment of black people, that would be somewhat outside of the framework of what I am talking about.
The construction here is, do Black Americans have worse outcomes, on average, because of themselves, or because of societies treatment of them. Culture would fall into the bucket of “they are the reason for their own problems”.
Obviously Nigerians do well on average, but they are also a small fraction of the population. Pointing to Nigerians and saying that race isn’t a contributing factor is making an argument after having found the statistical outlier that proves your argument, how do Nigerians compare to the top cohort of white Americans based on ethnicity or whatever? Is it possible that Nigerians would actually be doing better were there not racial barriers?