jmm99,

Sub-Saharan Africa has far more ancestral significance to Americans; in 2010, 38.9 million African-Americans (12.6% of total pop.) (Wiki).

Looking at it from an economic standpoint, the US has little reason to be involved in the MENA countries, Sub-Saharan Africa and Central/South Asia ($122 billion), as compared to much more important regions and countries.
I don't think the "ancestral significance" has ever amounted to much - or will ever amount to much in future. This isn't the Israeli lobby in the United States - these are people cut off from their roots - i.e. they know their ancestors came from Africa, but they don't know exactly where, so the links aren't that strong.

The figures don't lie - US is destined to be a marginal player in Africa. I expect its share of African trade to decline as the years go by - and also its interest in the continent.

If Al Qaeda & its affiliates weren't roaming around the Sahel, US would have forgotten about Africa - a long time ago (it has its oil & gas concessions, it would do the usual unimaginative NGO/Aid routine - & that's about it).