I will only respond this one time because you can't restrict a person from being stupid. You aren't making sense. Observe.
The US has about 2 million soldiers and our soldiers are better trained and equipped then African soldiers.
It doesn't matter. They aren't enough. Do you know how many a billion people are? 2 million soldiers are not enough to hold even the single country of Nigeria with 100 million people.
China and Russia would be hypocritical...
Yes, they would be, but they still won't stand by and allow America do it, hypocrital or not. China and Russia need raw materials from Africa, they currently have investments and agreements with several African countries, they would be crazy to allow America freedom to attack and take over Africa.
I think the US military is stronger then all 3 (India,China, Russia)of their militaries put together,
Then you are either young and very ignorant, or you are just stupid. The US is stronger than EACH one of them, but cannot fight all of them simultaneously. That is not something a knowledgeable person would think.
Then what was all the other land for?
It was for the taking as there were no organized countries to oppose their taking.
I think there were other tribes on the continent before Europe came along.
Who do you think it would be easier to invade, an area with a few scattered tribes with bows and arrows, or an actual country with an actual military with jets, bombs, and tanks? Europe did it when there were just tribes. America would have to do it multiple times to a real and active militaries. And each time America would have to leave a chunk of their soldiers there who would be useless in the attack on other countries. This would happen more than 50 times, and they began without enough soldiers. Think man.
If the locals are okay with it, which they probably would be if the US increases the standard of living for them and doesn't treat them badly, then the military will only have to defend the area from outsiders.
Are you stupid? OK with "it"? Would you be "OK" with someone invading your country? The African soldiers that would be killed, who do you think their mothers and fathers will be? Do you think promising their brothers and sisters a better standard of living would make them OK with America invading their country and killing their family? Would you be OK with your dad and brothers being killed and your country taken over if your standard of living would be made "better"?
Keep in mind that the African military, once the consent of the people is obtained, probably would help the US military in defending the area.
Because the American army is going to hold a vote? And the African army defending their country are going to wait till there has been a vote? What country's army do you think would help an invading army?
They aren't well equipped compared to American soldiers,
Doesn't matter. There are too many of them. Plus, the African soldiers will be home, so will not need as much logistics as the invaders. American soldiers will still die, no matter how much more better equipped they are. And after America loses the element of surprise, more of them will die with each successive invasion.
Africa may have some bombs and fighter jets, but the US has much more of them
Doesn't matter. America doesn't have enough of them. And each plane or tank lost in battle will delay the next invasion.
...and the US can make more on demand.
Not fast enough.
If Africa loses a tank, it would take a long time to make a new one.
Russia, China, and India would supply the African countries instantly.
If America loses a tank, they could make 5 more.
But when they lose soldiers, of which they already don't have enough, they can't make 5 more. And they would lose soldiers. The idea is ludicrous.
How old are you by the way?