Compare the two and you will see their spending on all needs and wants is different. It won't just be the food they eat. One will plan long term for their gratification and the other will simply take what they can afford right now, that later comes from always having that option.
Go look back a hundred years or more when the Irish; my ancestors; got here. Many came here in debt to others working bare subsistence levels and they would have similar habits to your Ghanians, as in tomorrow isn't a guarantee so plan for the worst. I expect that the second generation after the move the attitudes will change but that is heavily influenced by culture
My step-father, who is a Mexican immigrant, started laughing. He said that's all they ate growing up. He said it wasn't until high school when his dad got a job in a General Motors factory that they had enough money to eat hamburger and cheese along with their beans and rice.
Personally I think the African American community could use less BLM and more of the values and ideals of these migrant groups.
African migrants, unless they came as refugees, were usually upper middle or higher class - with college degrees and some degree of wealth in order to get here. They're typically not the average African, socioeconomically speaking.
Most Africans also haven't been weighed down by system racism their whole lives. For example, a Ghanaian friend told me that how never really understood racism until he moved to the US in his 20's as he had never experienced it in Ghana.
The african american neighbors are extremely obese and _constantly_ eating McDonalds (I can tell from the litter I clean up in the parking lot...). My ghana immigrant neighbors on the other hand are skinny as rails and can be seen hauling 10 pound bags of rice/beans/etc. into their house.
It's often overlooked, but there's more than just money that passes between generations. Simple knowledge like "how to cook with unprocessed foods" is extremely valuable information to pass on to offspring. We need to somehow tackle that if we ever plan to help people entrenched in inter-generational poverty.