1. Sub-saharan Africa didn't develop any written language
This is simply incorrect. A prominent example of the Ge'ez script. But there are several others.
2. They couldn't even invent the wheel (in sub-Sahara Africa)
Anyone who says this doesn't know how wheels work.
They did have the wheel, but it was of no use to them. In order to use wheels for transport you need a lubricant. In Europe, Asia, and North Africa they had the wild boar (and later the domesticated pig). These were animals with a lot of fat which could be used to lubricate those wheels. But they are not native to Sub-Saharan Africa. Without sufficient and cheap fat wheels were useless. It's why places that didn't have easy access to fat didn't use wheels.
Even with our modern technology we still need to use lubricants... If anyone thinks a pre-industrial civilization could fix this issue, which we still can't fix today, needs to lower their expectations.
On top of that, Africa has a lot of rivers and African river ships were so incredibly advanced that when Europeans tried to invade Africa in the 16th-18th centuries that they were easily defeated by the local Africans.
3. Africa didn't have any countries/empires
Even a short google search easily disproves this.
Here are just 20 of them: Mali Empire, Ghana Empire, Songhai Empire, Kanem-Bornu Empire, Sokoto Caliphate, Jolof Empire, Oyo Empire, Benin Empire, Kaabu Empire, Aro Confederacy, Ashanti Empire, Kong Empire, Bamana Empire, Wassoulou Empire, Kongo Kingdom, Luba Empire, Lunda Empire, Zulu Kingdom, Maravi Empire, Rozvi Empire.