Emira Woods, of the Institute for Policy Studies, told Al Jazeera that the US plan was really to secure its oil supply.
"Clearly I think Africom is really to secure oil and to contain China and I think the US is really creating this next Cold War where China becomes the next big foe.
"The rest of the continent is extremely worried after having seen Iraq where first you had oil, then you had the military and what resulted was a disastrous foreign policy."
Following similar criticism, the US clarified the proposal, saying Africom would not bring any more US troops or bases to the continent.
A base for 1,800 US troops already exists in Djibouti.
"That doesn't mean that we won't try to develop some kind of office in Africa. We haven't made our minds up. It's a new concept," Bush said alongside John Kufuor, his Ghanaian counterpart.
"It is a command structure that is aiming to help provide military assistance to African nations, so African nations are more capable of dealing with Africa's conflicts, like peacekeeping training," he explained.
The US president also rejected concerns about a growing rivalry with China in Africa over access to the continent's oil, metals, and other raw materials, saying Beijing was not a "fierce competitor".
"I don't view Africa as zero-sum for China and the United States. I think we can pursue agendas without creating a great sense of competition," Bush said.
Kufuor warned against trying to "ostracise" China, which he said was "coming not as a colonial power, as far as we can see. It's coming, if I may put it, as a guest, and I believe on our terms, on the terms of the African nations".
Kufuor also said he accepted Bush's explanation on Africom and said it should "put paid" to the rumours that the US is seeking to expand its influence on the continent by constructing new military installations.
Bush was due to conclude his African tour on Thursday in Liberia, which has offered to host Africom's headquarters.