Look at the size of the country (around 1/3 of USA) and the number of people living there (112M according to wikipedia), also 1/3 of USA. So the density should be about the same but when you look at satellite photos it's one giant city (18M), several smaller cities and the endless forest. Can it support other 90M people?
So yea, DRC can easily be like that. Especially if they don't subscribe to 4-6 people living in a house thing that the US does.
If you looked at US infrastructure and based the population we should have on how a developing nations population works, then you'd come up with a number like 750 million to a billion people... because 6 to 10 people live in a house, right? FYI, average US household is 2.5 people.
Simply put you cannot make any of your assumptions without more knowledge.