The Kenya and Ethiopia debate has been going on for a long time.
However i'd like to look at the different training methods. It seems that the Kenyan's signature workout is a fast-paced long run or a gruelling fartlek. Then in races you can see it, they go out fast, paces bouncing up and down and have great mental strength and endurance. Then when you look at Ehiopians, they seem to do loads of drills a lots of hills and strength training while doing a lot of speed endurance interval sessions. Then in races they often outkick the Kenyan's or if they try to push from the start they often can't keep it up for a long time. Let's take Kamworor for example and then Gebriwhet. Of course there's outlier but it's interesting to look at the different effects of training.
Meanwhile American's and Britains seem to do loads of race pace training so can keep up great pace but never want to increase the pace and lack the basic cardiovascular endurance. Not saying there isn't great American's or Britains but it's something to think about.