The US, in an utterly embarassing display of weakness, has one guy qualify to participate in the 2000 Olympic marathon. Four years later, in frigid and abysmal conditions, the US marathoners run amazingly well and the US has no problem qualifying it's entire contigent (reserves included). Increadible effort? Probably. Short course "certified" by a USATF trying to avoid further embarrassment? ....
*Note: This theory is backed up by exactly zero evidence and is proposed merely b/c I am bored.