How do you get actual reports from places that don't even have hospitals let alone testing or ways of keeping track of that sorta thing? These are places that barely have a government or in some cases simply don't have any government. The U.S and Canada have high numbers because there are actually people counting.
Plus as
@RonD pointed out, people in these places aren't out traveling and partying every day. They are busy farming dirt. Not a huge influx of people are traveling too these places either cause well... why would you? It's super easy to self isolate when your poor, have no where to go, no way to get there, and no one wants to be near you...
And as a third point, most people from 1st world nations are too stubborn to let the slightest thing inconvenience them like wearing a mask in the grocery store or not going out clubbing. People in these third world countries have alot of experience with being ravaged by disaster.
So its most likely a mix of no one counting, good social distancing by design, and the general ability to be able to handle a crisis without complaining that gives a place like Ethiopia better numbers than the U.S.