Since being the MVP of the winning team in WWII, America has been playing the WHOLE map of the world.
US interests reach every corner of the world. And to protect our vast interest we have created an immense infrastructure.
If you look at the map in the link, the US does not lack interest in Africa.
In fact the US is very interested in Africa. The only problem is, we are also very interested in the Middle East, Central America, Eastern Europe, Western Europe, the Mediterranean, Latin America, Central Asia, Southeast Asia, the Pacific Rim, the Korean Peninsula, etc.
And because we have so many interests, it is very hard even for a great power like the USA to focus its attention on any particular region for an extended period of time. Notice the Middle East requires our constant attention. And after the Middle East, we really only have the energy and power to focus on at most two more regions at a time.
Western Europe on the other hand has lost most of its global influence and power projection as a result of WWI and hit absolute rock bottom after WWII. It has lost its colonies in the Americas, Australia, Africa, and Asia. Africa is the only place where the EU (notably France) still has substantial influence. Consequently, the EU is now playing a very small corner of the map, and can focus much of its attention on where it actually plays.