There haven't been many American KLM pilots during the last seventeen years, but there have been a few. A couple left around the turn of the century, but it was supposedly for greener pastures and better flying jobs in the us, which were good at the time. As far as I know, there was never a buyout package. I do know of one canadian who was able to keep his senority for awhile when he went back to canadian airlines, though. Of course you could lose your medical in one country and still be able to fly in another, but I have always found the european medicals very fair, and at the moment it is cheaper for me to do my faa medical in holland than in the us.