Harry

Well, it's true that it's ultra-unlikely that you will get actually hired before you move to the U.S. However, it could be worth getting in touch with people before you move here in order to build contacts. That's what I did, never got offered a job before I moved here, but was working within one month of moving here for one of the companies I had been talking to. A year later that job seemed to be going nowhere so I jumped ship - to another company I had been talking to before I moved here!
I don't know if you guys have any visits planned before you actually move, but if you do I'd definately try to get in to meet some people.
Anyway, best of luck with everything!

-Harry