So much in the relay depends on the exchanges.
Assuming that the exchanges go well for both the USA and Jamaica, I still think Jamaica will win, somewhat comfortably.
Although Carter hasn't been spectacular this year, he is every bit the equal of anybody the USA can put on leadoff.
Bolt and Blake are faster than Gatlin and as fast as Gay on a relay leg.
And whomever else runs for Jamaica, be it Powell or Frater, is at least as good as Bailey, Demps, or Patton on second leg or anchor. Frater can be really good on that second leg.
I agree that the USA is better than they showed in Monaco--Gat to Gay will be better when Gay decides to employ a start, and Gat can go a bit faster than he did IMO. But with everyone at their very fastest, the Jamaicans are a faster team.
Are you suggesting that the Jamaicans are not at their fastest? Powell wonky? Bolt still injured? We'll see, the only top guys I have full faith in are Gatlin and Blake--and possibly coincidentally, they are the only 2 big guys who have served PED suspensions.