When US marathoners were among the best in the world our best distance runners were running the event. In '72 Shorter, Moore, and Bacheler were all international class distance runners. In '76 Shorter was there again and Don Kardong had been a solid 5,000 guy. Rodgers was never much for the track but Bill Squires always said he could have been one of the best if he'd taken track seriously. Getting third in World Cross Country supports that argument. Salazar, Craig Virgin, both international class track runners. Greg Meyer was a sub 4:00 miler.
By 1990 we'd gotten away from having our best guys run the marathon and we reverted to the pre 70s where the best guys stayed on the track and either ignored the marathon or maybe ran it as a "back up" event to be sure they made an Olympic team, e.g. George Young in '68. If someone is unhappy with how US marathon runners are placing in big events it's useless to criticize guys like Fauble, Albertson, Hehir, etc., etc., etc., who are guys making the most of the abilities they have. If you want competitive US marathon runners in big events you need to get guys like Fisher, Kinkaid, Klecker, etc., running marathons seriously. It's what happens in Japan, nearly any young runner who shows potential begins training for marathons. That's a big part of why their track times aren't as good as ours. We did it with Galen Rupp. It seems unlikely to happen here now because economically guys like Fisher are probably better off on the track.