I respect USA's soccer, and I feel they are going to be real good in two more WC. But I have also seen a lot of both USA and Costa Rica, and I feel that they are not at their top level right now.
Costa Rica is in the same group as germany, poland and Ecuador. Ecuador clasified to the World Cup third behind only argentina and Brazil in South america. Germany are playing at home and despite their low game, they still are not about to lose at home. Costa Rica just got embarassed, and I mean embarassed by an african team
USA is in a tough group. Ghana has been improving as of late, and I think everyone is just writing them of as an easy victory, and it will not be, Italy is maybe not at its top but never easy, and czech will be good, and if not injured can be better than a lot of teams in the WC.
Which means that in my opinion to do better than Costa Rica, Sweden, Netherlands, Ukraine and Croatia, just have to make it to the second round. Sweden will make it no problem, Croatia will make it under Brazil, Ukraine under spain. And the only one I have to worry about is Netherlands (not because they are worse than the US but because playing in that group, anyone can win it... US in that group would not stand a chance).
If all four teams make the second round. Then I have to put the only but in this competition, that is that if one of those teams has to face another one in the second round and they are eliminated, that does not count... See if Ukraine and Sweeden have to play each other and one of them is out, then I believe you cannot argue that particular matchup can't count (kinda like if Costa Rica threw the US out in the second round and all my guys moved on).
I think it is a safe bet, they have the odds, but I still think that it is in my favor.