We've seen an 18 year old teenager race sub-1:55, Pamela Jelimo. In Kenya, they historically do well in 800, 1500, 3000SC and Marathon. In USA, we historically do well in 100, 200, 400, 110H and 400H. In USA, females who are able to race 400m in 52 seconds or faster most often race 400m or 400mH. NCAA D1 schools love females who race 52 for 400m. There is little incentive for a USA teenage female to switch to 800m if she has 52 400m speed. In Kenya, since they have an 800m culture, a 52 second 400m runner such as Jelimo did not have a cultural barrier to moving up to 800m. This same argument holds for USA male 46 second 400m men. Most 46 second 400m men in USA will race 400m or 400mH in college. Kenyan male 46 second 400m runners have no cultural barrier to moving up to 800m.