Well, the chances of him getting a top airline job are not as high as if he was younger, and he will struggle to get "experience comensurate with age." However, there are people in their forties who get airline gigs so 32 isn't too old, it may just be more difficult.
IMO, if it's what he wants to do, then he should give it a go. Better to have tried and failed than to have never tried at all. He would also be an ideal candidate for a mid-level turbo-prop type airline (QANTAS link, Air NZ link, etc) as he would be more likely to look at a job like that as a career rather than a stepping stone.
It can be done, and it has been done. My first flight instructor was a nurse up till she was in her early 30s when someone bought her a trial flight and she switched careers. She had a job with Ansett NZ before it collapsed.
I don't have an opinion about whether he should go to the US or not as I don't know much about it.