No sure if this is helpful, but the other key factor here is who you know. I cannot overstate the importance of name recognition and charm. Attend the national conference in the US of the specialty you are interested in. Even better, present at one. Get to know other folk interested in what you are. As for advice from people you meet there, get yourself a mentor or friend. They can open doors for you to rotations and experiences in the US, that aren't advertised. Any american experience is good. Especially if they let you be more than an observer.