Agreed that if US runners are going to keep up with the rest of the world, they need to run faster.
But the individual and cultural advantages in the US for a US runner to try to run 205 are not significant enough to get individual marathoners, and large numbers of runners/non-runners in the general population to try for this.
Advantages in terms of relative monetary, social, etc. rewards are not there for US runners when the risks and effort required to run 205 are considered.
There may be, and likely have been, US marathoners that want to run 202, but they have not been able to do it.
The bar for relative running success for a US marathoner is rather low at perhaps 211 right now. This gets you some type of shoe deal, invitations and appearance fees at US races, a good shot at making the olympic team, some name recognition among the US running population, a chance to win US only prize money in races, perhaps some minor endorsement deals etc.
The incentives for the 211 marathoner to run 209 or 205 are not worth that much more.
Contrast this with a Kenyan 209 marathoner, who is a relative nobody. Their bar for any level of success is is so much higher, 205 or below, to achieve anything similar to the relative level of success of a 211 US marathoner.
It does not help that the culture of US marathoning, the US perception of marathoners, and our biggest marathon race courses (NY and Boston) reward finishing place more so than legal fast times. A 209 marathon on the right day will likely get a US male top 3 in The Olympic trials, a good chance at an olympic medal, and a top finish at NY or Boston. All of these get more attention than a sub 205.