But for many people on the continent, America's role appears to be a distant, nebulous one, increasingly overshadowed by that of another emerging global super-power.
Here in Lesotho, the Chinese are in almost every village - from the cornfields of the western lowlands right up to the snow-dusted peaks of the mountainous east.
In Nazareth, halfway up a steep hillside an hour's drive out of the capital Maseru, a cluster of people were gathered at the door of the local store. A young woman from southern China was helping a farmer to load supplies into a pickup truck.
"It's good here. The air is much cleaner than back home," she said, politely declining to give her name.
Inside, her Chinese colleague was manning the cash register with China's CCTV News playing on a television nearby. The only American brand visible came in the form of a handful of Coca Cola bottles in a fridge.
"I've been here two years. My relatives were already here. Business is okay. I feel the Basotho people respect us, to a certain point, because we do help out and they think we're okay as people," said the shopkeeper.
Some locals grumble about the influx of "Ba-China" - the Chinese - saying they are taking away jobs, and undercutting local businesses.
But many quietly acknowledge the entrepreneurial spirit and resourcefulness of the mainland Chinese and Taiwanese business people whose presence is strikingly obvious in this small nation of some two million people.
"American investors don't come to Africa.... I don't think they know much about this region, and we need to try and show them what we are, what we do. The Chinese are everywhere. I think they are great explorers," said Motebang Mokoaleli, from Lesotho's National Development Corporation.
But if American business people are thin on the ground in Lesotho - and the only one we could find was running the local grain mill - it does not necessarily follow that American influence is small here.
The biggest employer in the country is the garment manufacturing industry, housed in warehouses on the edge of Maseru. Some 40,000 locals are currently working here, many for wages of little more than $3 (Â£2) a day.
None of the workers I spoke to had any idea that the tracksuits they were stitching together were all heading for the United States.
Their work is a direct result of America's African Growth and Opportunities Act (Agoa), which offers tax breaks to support manufacturing in a select group of African countries and is single-handedly responsible for the garment industry's success in Lesotho.
But, unsurprisingly, it is business people from the Far East, and in particular from Taiwan, who are taking advantage of Agoa to build and run the sector in Lesotho.
"This is my second home now," said Jennifer Chang, owner of the Shinning Century factory.
"We're not the enemy. We want to get the benefit, but we also benefit our team, our employees. This past 10 to 15 years we see a big change here - people are able to have education," she said, praising an American initiative that "makes countries develop - not just [through] aid".
On the far side of town, perhaps 50 people had gathered at an HIV-Aids clinic for check-ups. Here, too, was another example of America's hugely significant, but largely arms-length, support for Lesotho.
Through a range of programmes, not least the long-running Pepfar initiative, the US has poured huge sums into fighting the virus, which is currently thought to affect some 23% of the population (the second highest rate in the world).
"Generosity. The Americans have been very generous in helping Lesotho. I think without the US things would be dismal, to say the least.
"A lot of people would have died long ago because many people in this country cannot afford antiretroviral treatments for HIV," said Dr Edith Mohapi, the head of Baylor College of Medicine Children's Foundation Lesotho.
Some people, harking back to the colonial "scramble for Africa", see China and the US locked in a new contest for resources.
Perhaps it will come to that, but in Lesotho, as in many parts of the continent, the world's two biggest economies seem to be playing different, and in some respects complementary, roles.
As US President Barack Obama visits East Africa this weekend there is an understandable focus on issues like security and counter-terrorism, as well as entrepreneurship.