Americans and Europeans will continue to be mediocre at the marathon for as long as they view the event simply as a way to prolong their career. The US and Europe sends washed up track stars to the event and expect to compete with Kenyans and Ethiopians who have been running marathons since the age of 18-22. The East Africans have the experience and are at their physical peak, competing against inexperienced Americans and Europeans who are past their prime. And we wonder why they dominate the event.
Mantz is a genuine hope for the US because he's focussing on the marathon right away. I think he'll run 2:05 eventually if he stays relatively injury-free. For the UK, I'm hopeful for Emile Cairess. He's 25 and focussing on the roads and has a world class coach in Canova. I think he can debut at 2:07-2:08 and work his way down from there